Overview
The thyroid gland is the largest endocrine gland in the body and is located under the thyroid cartilage immediately in front of the third and fourth cartilage rings of the trachea, consisting of two lobes and the isthmus. The thyroid gland is followed by four parathyroid glands and the recurrent laryngeal nerve. The main function of the thyroid gland is to synthesize thyroid hormones and regulate the body’s metabolism. 100-200μg of inorganic iodine compounds are present in the daily food of the average person, which are absorbed into the bloodstream through the gastrointestinal tract and rapidly absorbed and concentrated by the thyroid gland, which stores about 1/5 of the body’s iodine. /When iodide enters the cells, it rapidly binds to the tyrosine group on the thyroglobulin molecule in the glial cavity through the action of oxidase, forming monoiodotyrosine (MIT) and diiodotyrosine (DIT), iodinated tyrosine.
Post-thyroidal view
The synthesized thyroxine (T4) and triiodothyronine (T3) are secreted into the circulation by oxidative enzymes, and are mainly bound to thyroxine-binding globulin (TBG) in the plasma for transport and regulation of blood Thyroxine Thyroxine (T4) is deiodinated in peripheral tissues to form the biologically active T3 and the biologically inactive rT3, respectively, and the deiodinated iodine can be reused. Therefore, in hyperthyroidism, blood T4, T3 and rT3 are all increased, while in hypothyroidism, all three are below normal values. Thyroxine secretion is regulated by pituitary cells and TSH through the adenylate cyclase-cAMP system. TSH is controlled by TRH, which is secreted by the hypothalamus and forms the hypothalamic-pituitary-thyroid axis that regulates thyroid function.
The thyroid gland has two layers of peritoneum: the pre-tracheal fascia wraps around the thyroid gland to form the thyroid sheath, called the thyroid pseudo-peritoneum; the outer membrane of the thyroid gland itself extends into the parenchyma of the gland and divides the gland into several lobes, called the fibrous capsule, also called the true thyroid peritoneum. The interstitial space between the glandular sheath and the fibrous capsule contains loose connective tissue, blood vessels, nerves and parathyroid glands. The thyroid gland should be surgically separated within this space to avoid damaging structures that should not be damaged. At the upper end of the right and left lobes of the thyroid, the pseudoperitoneum is thickened and attached to the thyroid cartilage, called the thyroid suspensory ligament; the pseudoperitoneum on the medial side of the right and left lobes and behind the thyroid isthmus is healed by the cartilage of the cricoid cartilage and the tracheal cartilage ring, forming the lateral thyroid ligament. These ligaments hold the thyroid gland to the wall of the larynx and trachea, so that the thyroid gland can move up and down with the larynx during swallowing, which is the basis for determining whether the thyroid gland is enlarged. The laryngeal nerve often passes behind the lateral and suspensory ligaments of the thyroid gland, so it is important to avoid damaging the laryngeal nerve during thyroid surgery.
The anterior aspect of the thyroid gland is composed of the skin, superficial fascia, superficial cervical fascia, subglottis muscle group and anterior tracheal fascia in order of superficiality. The posterior medial aspect of the thyroid lobe is adjacent to the larynx and trachea, pharynx and esophagus, and the recurrent laryngeal nerve, and its posterior lateral aspect is adjacent to the carotid sheath and the common carotid artery within the sheath, the internal jugular vein and vagus nerve, and the cervical sympathetic trunk located deep within the anterior fascia. When the thyroid gland is enlarged, if it is compressed medially, it may cause difficulty in breathing and swallowing and hoarseness, etc. If it is compressed posteriorly, it may cause HORNER syndrome, such as narrow pupils, ptosis and sunken eyes.
Thyroid tumors
Thyroid tumors can be divided into benign and malignant tumors. In clinical practice, thyroid tumors often appear only as thyroid nodules, so they are often confused with thyroid nodules. In fact, nodules are only a morphological description. They include tumors, cysts, masses of normal tissue, and thyroid masses caused by other diseases. It is difficult to determine the nature of thyroid nodules clinically, and even on pathologic biopsy, it is sometimes not easy to clearly identify thyroid adenomas from nodular hyperplasia and benign tumors from malignant tumors. Therefore. The incidence of thyroid tumors is not easy to accurately count.
Thyroid tumor is a common disease and its incidence rate varies greatly in different regions. Generally the incidence of thyroid tumors is higher in areas where goiter is endemic than in non-endemic areas. The most common type of thyroid tumor is benign thyroid tumor. Thyroid cancer is uncommon, but has been increasing yearly in recent years. Surgically proven single nodules are benign tumors in 80% and malignant tumors in 20%. The incidence of tumor in single nodule is 15.6%-28.7%, while the incidence of cancer in multiple nodules is generally less than 10%. This means that a single nodule is several times more likely to be cancerous than multiple nodules. In terms of gender, thyroid tumors are mostly found in females and their incidence rate is 4 times higher in females than in males, but in terms of the ratio of thyroid cancer to thyroid nodules, males are higher than females. In each age group, the incidence rates of benign and malignant thyroid masses are similar, but among thyroid nodules in childhood, the incidence rate of thyroid cancer is high, accounting for about 50%-71%, therefore, for thyroid nodules in childhood, one should Therefore, it is important to be especially alert to the possibility of cancer in children.
Thyroid disease
When you notice thickening or a lump in your neck, even if there are no uncomfortable symptoms, you should think about whether an enlarged thyroid gland or other thyroid disorders have occurred. You should go to the hospital promptly at this time. Your doctor can usually tell you whether your thyroid gland is enlarged and whether there is a lump by palpating the thyroid gland. There are many different thyroid disorders, and those who have an enlarged thyroid gland or a swollen thyroid gland generally need further tests to determine the nature of the thyroid disorder, such as blood tests to check thyroid function and, if necessary, radionuclide and ultrasound examinations of the thyroid gland, or even cytology of thyroid puncture. You should think about the possibility of hyperthyroidism when you have symptoms such as fear of heat, excessive sweating, palpitations, anxious temperament, hyperphagia, and weight loss. When you notice symptoms such as fear of cold, swelling, weight gain, dry skin and loss of appetite, you should be aware of the possibility of hypothyroidism. When you feel pain and fever in the neck, especially when you can feel a lump in the thyroid gland and have pressure pain, you should think about the possibility of acute or subacute thyroiditis. If you encounter any of these conditions, you should visit the endocrinology department of the hospital in time for further examination so that you can get timely diagnosis and reasonable treatment.
Disease classification
1.Simple goiter
2. Hyperthyroidism (complications of hyperthyroidism)
3, hypothyroidism
4.Thyroid nodules, thyroid adenoma
5.Acute septic thyroiditis
6, subacute thyroiditis
7, chronic lymphocytic thyroiditis
Thyroid gland is a common endocrine disease caused by the enhancement or weakening of thyroid gland function and the synthesis and secretion of too much or too little thyroid hormone due to various reasons, mainly including: hyperthyroidism (commonly known as hyperthyroidism), hypothyroidism (commonly known as hypothyroidism), thyroiditis, goiter, goiter, thyroid tumor, and thyroid cancer.
I. Hyperthyroidism
Hyperthyroidism refers to a high functional state of the thyroid gland, characterized by enlargement of the thyroid gland, proptosis, increased basal metabolism and autonomic nervous system disorders. The disease is most common in women, with a ratio of 1:4-6 between men and women, and is most common between the ages of 20 and 40. The most common clinical form of hyperthyroidism is toxic diffuse goiter.
Main pathological manifestations and hazards.
(1) Hypermetabolic syndrome: Patients may present with fear of heat and sweating, red and sweaty skin, palms, face, neck and axillary skin. There is often hypothermia, and in severe cases, hyperthermia may occur. Patients often have tachycardia, palpitations, and marked hyperphagia, but weight loss and fatigue.
(2) Enlarged thyroid gland
(3) Ocular signs: protruding eyes
(4) Nervous system: hypersensitivity, agitation, irritability, insomnia and nervousness, talkative and hyperactive, sometimes inattentive, sometimes indifferent and depressed.
(5) Cardiovascular system: palpitations, chest tightness, shortness of breath, aggravated by activity, various premature beats and atrial fibrillation may occur.
(6) Digestive system: hyperphagia and significant weight loss.
(7) Reproductive system: Female patients often have reduced menstruation, prolonged cycles, or even amenorrhea, but some patients can still have pregnancy and childbirth. Men are more impotent, and some have breast development.
II. Hypothyroidism
Hypothyroidism is a systemic disease caused by insufficient synthesis and secretion of thyroid hormone or poor physiological effect of thyroid hormone and insufficient physiological effect.
It is mainly divided into: cretinism, juvenile hypothyroidism and adult hypothyroidism, mostly seen in middle-aged women. Hypothyroidism in adults is caused in many cases by surgical removal, long-term antithyroid drug treatment or treatment of hyperthyroidism with radioactive 131 iodine.
Main pathological manifestations and hazards.
(1) General manifestations: fear of cold, dry skin with little sweating, roughness, yellowing, coldness, thinning hair, dryness, brittle and cracked nails, fatigue, drowsiness, poor memory, mental retardation, unresponsiveness, mild anemia, and weight gain.
(2) Special manifestations: pale and waxy face, swollen face, dull gaze, puffy eyelids, indifferent expression, little speech, hoarse speech, slurred speech.
(3) Cardiovascular system: slow heart rate, low heart sound, generalized enlargement of the heart, often accompanied by pericardial effusion, swelling of myocardial fibers, deposition of mucus glycoproteins (PAS staining positive) and interstitial fibrosis after the disease, called hypothyroid cardiomyopathy.
(4) Reproductive system: Men may have lower sexual function, delayed sexual maturity, delayed paraphilia, decreased libido, impotence and testicular atrophy. Women may have menstrual irregularities, excessive menstrual bleeding or amenorrhea, and are generally infertile. There are effects on fertility in both male and female patients.
(5) Muscle and joint system: muscle contraction and relaxation are slow and delayed, muscle pain and stiffness are often felt, bone metabolism is slow, bone formation and resorption are reduced, joints are dysfunctional, there is a feeling of tonicity, aggravated by cold, as in chronic arthritis, and joint cavity effusion is occasionally seen.
(6) Digestive system: Patients have decreased appetite, constipation, abdominal distension, and even paralytic intestinal obstruction, and about half of the patients have complete gastric acid deficiency.
(7) Endocrine system: impotence in men, excessive menstruation in women, amenorrhea in patients with prolonged illness, low adrenocortical function, and reduced blood and urine cortisol.
(8) Psychoneurological system: memory loss, mental retardation, unresponsiveness, drowsiness, depression, and sometimes psychotic manifestations, and in severe cases, the development of suspicious schizophrenia, late dementia, cyclothymia, or lethargy.
Three, thyroiditis
Thyroiditis is a thyroid disease with inflammation as the main manifestation.
It is divided into: Hashimoto’s thyroiditis, subacute thyroiditis, painless thyroiditis infective thyroiditis and other causes of thyroid, most commonly chronic lymphocytic and subacute thyroiditis, in order of incidence.
1. Hashimoto’s thyroiditis
Hashimoto’s thyroiditis was first reported and described in 1912 by a Japanese man named Hashimoto, hence the name, also known as Hashimoto’s disease, chronic lymphocytic thyroiditis, and autoimmune thyroiditis. It is the most common type of thyroiditis, accounting for 7.3%-20.5% of all thyroid disorders. Hashimoto’s disease is most often seen in women aged 30-50 years and is also a common cause of sporadic goiter in children, with a male to female ratio of about 1:6-10.
Main pathological manifestations and hazards.
The onset of the disease is slow, and at the onset there is mostly an enlarged thyroid gland with a hard and tough texture and clear borders, and some patients may have symptoms of pressure.
A few patients may have transient hyperthyroidism in the early stage, but most cases are found to be under thyroid function.
Patients often show fear of cold, swelling, weakness, dry skin, abdominal distension, constipation, menstrual disorders, and loss of libido.
2. Subacute thyroiditis.
Most of them develop in 30~50 years old, and the incidence is 3-6 times more in women than in men. The majority of patients can return to normal thyroid function after Yu, but some patients can relapse again or repeatedly within a few months after remission. The incidence of permanent hypothyroidism is less than 10%, and very few cases may develop into Hashimoto’s disease or toxic diffuse goiter.
Main pathological manifestations and hazards.
The typical presentation is severe thyroid pain, which usually starts on one side of the thyroid gland and quickly spreads to other parts of the gland and to the ear and jaw, often accompanied by general malaise, malaise, muscle pain, and also fever, which peaks within 3-4 days after the disease and subsides within 1 week, or in many patients with a slow onset of more than 1-2 weeks, with fluctuations lasting 3-6 weeks, and after improvement, several times over several months The thyroid gland can be 2-3 times larger or larger than normal, and the pressure pain is obvious on contact. However, these symptoms do not last long and eventually the thyroid function returns to normal.
Thyroid nodules
The nodules on the thyroid gland may be thyroid cancer, thyroid adenoma, nodular goiter and other causes, but before their nature is clarified, they are collectively called thyroid nodules.
Main pathological manifestations and hazards.
Clinical manifestations are an enlarged thyroid gland and multiple nodules of varying sizes may be seen to be palpated, with the texture of the nodules being mostly moderately hard. There are few clinical symptoms, only discomfort in the anterior neck area. Thyroid function is mostly normal. However, some patients may develop secondary hyperfunction or cancer.
Most thyroid nodules are benign, of which only thyroid cancer is a malignant disease. However, 50% of nodules appearing in childhood are malignant, and when a nodule develops in a young male, the possibility of malignancy should also be alerted. If a new nodule or an existing nodule increases rapidly in a short period of time, malignant lesions should be suspected. High speed suspicion of malignant disease should be treated as soon as possible.
V. Thyroid adenoma
1.Thyroid adenoma: A common benign thyroid tumor that occurs in or near the middle of the neck. It is smooth, has clear edges, moves up and down with swallowing movements, has a firm texture, is not painful to press, and grows slowly.
2.Thyroid cyst: If the blood circulation of thyroid adenoma is insufficient and degenerative lesions occur in the nodule, causing cyst formation, it is called thyroid cystadenoma, or thyroid adenoma.
3. Hyperfunctional adenoma: If there is a combination of hyperfunctional symptoms, it is called hyperfunctional adenoma, also called toxic adenoma, which is less likely to become malignant.
4.Papillary adenoma: If there are papillary changes in the adenoma, it is called papillary adenoma, which is more likely to become malignant.
Thyroid cancer
Thyroid cancer is composed of several types of cancer with different biological behaviors and different pathological types, including papillary, follicular, undifferentiated and medullary carcinomas. Their age of onset, growth rate, metastatic pathways and prognosis are significantly different. For example, the survival rate of papillary carcinoma is nearly 90% at 10 years after surgery, while undifferentiated carcinoma has a very short course and usually survives only a few months.
The structure of thyroid gland
The thyroid gland is the largest endocrine gland in the body. It is brownish-red in color, divided into two lobes and connected in the middle (called the isthmus), with an “H” shape and about 20 to 30 grams. The thyroid gland is located on the anterior side of the upper part of the trachea in the lower part of the larynx and can move up and down with the larynx when swallowing. Although the iodine content of the gland is usually 25 to 50 times higher than that of the blood, 1/3 of the daily dietary iodine intake enters the thyroid gland, and 90% of the total body iodine content is concentrated in the thyroid gland. Thyroid hormone is a hormone secreted by the thyroid gland.
The physiological functions of thyroid hormones are: (1) Promoting metabolism, increasing oxygen consumption in most tissues, and increasing heat production. (2) Promote growth and development, which is essential for the development of long bones, brain and reproductive organs, especially during infancy. Lack of thyroid hormone at this time will suffer from cretinism. (3) Increases excitability of the central nervous system. In addition, it also strengthens and regulates the effects of other hormones, accelerates heart rate, strengthens cardiac contraction and increases cardiac output.
The thyroid gland is an important organ of the endocrine system, which is distinctly different from other systems of the human body (such as the respiratory system, etc.), but is closely related to the nervous system, interacting and cooperating with each other, and is called the two major biological information systems. The endocrine system includes many endocrine glands, which can be stimulated by appropriate nerves to release efficient chemical substances from some cells of these glands, which are sent to the corresponding organs at a distance through blood circulation to play their regulatory role. The thyroid gland is the largest endocrine gland in the human endocrine system. It is stimulated by nerves and secretes thyroid hormones, which act on the corresponding organs in the body to exert physiological effects.
Most people do not know where the thyroid gland is located, but most people are not unfamiliar with “thick neck disease”, which is actually an enlarged thyroid gland, which tells us that the thyroid gland is located in the neck. To be more specific, the thyroid gland is located about 2 to 3 cm below the “laryngeal node”, which we can touch ourselves, and can move up and down with it when swallowing something.
The thyroid gland is shaped like an “H”, brownish red, with two lateral lobes, left and right, connected by an isthmus. The two lateral lobes are attached to the lower part of the larynx and the upper side of the trachea, reaching the middle of the thyroid cartilage and the sixth tracheal cartilage, with the isthmus mostly located in front of the second to fourth tracheal cartilage, and some people are not developed. Sometimes a cone-like lobe protrudes upward from the isthmus, varying in length, with the longest reaching the hyoid bone, a vestige of embryonic development that often degenerates with age, making it more common in children than in adults.
The thyroid gland is covered with a fibrous capsule, called the thyroid capsule, which extends into the glandular tissue and divides the gland into lobes of varying sizes.
The thyroid gland matures during puberty and weighs 15 to 30 grams. The two lateral lobes each have a width of about 2 cm and a height of 4 to 5 cm, and the isthmus has a width of 2 cm and a height of 2 cm. The thyroid gland is slightly larger in women than in men. Under normal circumstances, the thyroid gland is neither visible nor palpable in the neck because it is very small and thin. If the thyroid can be felt in the neck, even if it is not visible, the thyroid is considered to be enlarged. This degree of enlargement is often physiological, especially in women during puberty, and is not usually the result of disease, but sometimes it can be pathological.
The human thyroid gland weighs 20 to 30 g and is the largest endocrine gland in the body. It is located on both sides of the upper trachea, below the thyroid cartilage, and is divided into two lobes, which are connected by a narrower isthmus in the middle, in the shape of an “H”.
The thyroid gland is composed of many follicles. Microscopically, the follicles consist of simple cuboidal glandular epithelial cells surrounded by a central follicular cavity. The epithelial cells are the site of thyroid hormone synthesis and release, and the follicular cavity is filled with a homogeneous gelatinous substance that is the thyroid hormone complex and the reservoir of thyroid hormones. Changes in follicular morphology reflect the functional status of the gland: when glandular activity is reduced, the adenosepithelial cells are flattened and the follicular lumen stores increase; if activity is hyperactive, the follicular epithelium is columnar and the follicular lumen stores decrease.
Thyroid hormones
Two biologically active hormones secreted by the thyroid gland are thyroxine (also known as tetraiodothyronine, T4) and triiodothyronine (T3). They are a group of iodine-containing tyrosines that are synthesized in the thyroid gland cells using iodine and tyrosine as raw materials. The thyroid gland cells have a strong capacity to take up iodine. The human body takes in 100 to 200 μg of iodine from the diet every day, of which about 1/3 enters the thyroid gland. The total iodine content of the thyroid gland is about 8,000 μg, accounting for 90% of the total body iodine content, indicating that the thyroid gland has a strong iodine pumping capacity. When the thyroid gland is hyperactive, the iodine pumping capacity exceeds normal and iodine intake increases; when it is low, it is lower than normal and iodine intake decreases. Therefore, the ability of the thyroid gland to take up radioactive iodine (131I) is used clinically as one of the methods to routinely check thyroid function.
After iodine ions are taken into the epithelial cells of the thyroid follicles, they are rapidly oxidized to activated iodine by the action of peroxidase, and then iodinated by the action of iodinase to produce monoiodotyrosine (MIT) and diiodotyrosine (DIT) from the tyrosine residues in thyroglobulin. In this way, thyroglobulin containing the four tyrosine residues is stored in the follicular compartment (see the section on biochemistry).
When thyroid hormone is released by TSH, glandular epithelial cells first swallow the thyroglobulin in the follicular cavity into the glandular cells by swallowing it, and under the action of lysosomal protein hydrolase, the thyroglobulin is broken down. The number of T4 on the thyroglobulin molecule is much higher than that of T3, so T4 accounts for about 90% of the total amount of hormone secreted, while T3 is secreted in a smaller amount, but its activity is large, five times that of T4. The total amount of T4 secreted daily is about 96 μg, while that of T3 is about 30 μg. After T4 is released into the blood, part of it is combined with plasma proteins, while the other part is transported in the blood in a free state, and the two can be transformed into each other to maintain T4 and T3 are in dynamic balance in the blood, because only the free form can enter the cells to play a role. t3 is released into the blood, because the affinity with plasma proteins is small, mainly in the free form. About 50% of T4 is deiodinated into T3 every day, so the role of T3 cannot be ignored.
Biological effects of thyroid hormones
The biological effects of thyroid hormones are mainly in the following three aspects.
(i) Promoting growth and development
The most obvious role of thyroid hormones in promoting growth and development is during infancy, with the greatest impact during the first four months of life. It mainly promotes the growth and development of bones, brain and reproductive organs. Without thyroid hormone, the pituitary gland’s GH cannot function either. Moreover, in the absence of thyroid hormone, the pituitary gland also produces and secretes less GH. Therefore, congenital or early childhood deficiency of thyroid hormone causes cretinism. Patients with cretinism have short stature due to stagnant bone growth, and the ratio of upper and lower body lengths is abnormal, with the upper body taking up a larger proportion than normal. The dendrites, axons, myelin sheaths and glial cells of nerve cells are impaired, the brain is underdeveloped and the intelligence is low, and their sexual organs are not mature. When newborns have low thyroid function, they should be supplemented with thyroid hormone in appropriate amounts within one year of age, which is also effective for the development of the central nervous system and the recovery of brain function. Later than this period, even if a large amount of T3 or T4 is supplemented later, the normal function cannot be restored and the treatment is often ineffective.
(II) Effects on metabolism
1. The thermogenic effect of thyroid hormone can increase the oxygen consumption rate of most tissues and increase the thermogenic effect. This thermogenic effect may be due to the fact that thyroid hormone can increase the synthesis of Na+-K+ pump on the cell membrane and can increase its vitality, which is an energy-consuming process. Thyroxine increases the basal metabolic rate, and 1mg of thyroxine can increase heat production by 4000 KJ. The basal metabolic rate of patients with hyperthyroidism can be increased by about 35%; while the basal metabolic rate of patients with hypothyroidism can be reduced by about 15%.
2.The effect on the metabolism of the three major nutrients is very complex. In general, under normal conditions, thyroid hormone mainly promotes protein synthesis, especially protein synthesis of bone, skeletal muscle and liver, which is important for growth and development in early childhood. However, excessive secretion of thyroid hormone causes protein breakdown, especially in skeletal muscles, resulting in wasting and weakness. In terms of glucose metabolism, thyroid hormone has the effect of promoting the absorption of sugar and the breakdown of liver glycogen. It also promotes the utilization of sugar by peripheral tissues. In short, it accelerates sugar and fat metabolism, especially promoting the process of sugar, fat and protein decomposition and oxidation in many tissues, thus increasing the body’s oxygen consumption and heat production.
(iii) Other aspects
In addition, thyroid hormone also has an important role in the activity of some organs. It is important for maintaining the excitability of the nervous system. Thyroid hormone can act directly on the heart muscle to promote the release of Ca2+ from the sarcoplasmic reticulum, resulting in increased myocardial contractility and faster heart rate.
Regulation of thyroid function
(i) Hypothalamic-pituitary-thyroid function axis
The hypothalamic neuroendocrine cells secrete TRH, which promotes the secretion of TSH from the pituitary gland, the main hormone that regulates thyroid secretion. When an animal is depituitary, its blood TSH disappears rapidly, the rate of iodine uptake by the thyroid gland decreases, and the gland gradually atrophies, relying only on its own regulation (see later) to maintain a minimum level of secretion. Administration of TSH to such animals can maintain normal thyroid secretion. Cutting the connection between the hypothalamus and the pituitary portal vein, or damaging the hypothalamic thyrotropic area, both result in a significant decrease in blood TRH levels and a corresponding decrease in TSH, and thyroid hormone levels. This suggests a functional link between the hypothalamus-pituitary-thyroid gland.
The concentration of thyroid hormone in the blood often feeds back to regulate the TSH-secreting activity of the pituitary gland. When the concentration of free thyroid hormone in the blood increases, it will inhibit TSH secretion by the pituitary gland, a negative feedback. This feedback inhibition is an important part of maintaining stable thyroid function. When thyroid hormone secretion decreases, TSH secretion increases, promoting compensatory enlargement of thyroid follicles to supplement the synthesis of thyroid hormone to supply the body’s needs.
(B) Other stimuli in and out of the body
Various stimuli inside and outside the body can be transmitted to the center via receptors and afferent nerves to promote or inhibit the secretion of TRH by the hypothalamus, which in turn affects the secretion of thyroxine. For example, cold promotes thyroid secretion through the above link via skin cold receptors.
(iii) Self-regulation
Self-regulation of thyroid function refers to the regulation of thyroxine secretion by the thyroid gland itself in response to the amount of iodine supply in the absence of TSH or in the absence of a constant TSH concentration. When the iodine supply in food is excessive, it first inhibits the transport of iodine in the process of thyroid hormone synthesis, and also inhibits the synthesis process, causing a significant decrease in thyroid hormone synthesis. If the amount of iodine increases again, its anti-thyroid hormone synthesis effect disappears and thyroid hormone synthesis increases. In addition, excess iodine has the effect of inhibiting the release of thyroid hormones. Conversely, when the supply of exogenous iodine is insufficient, the iodine transport mechanism will be enhanced and the synthesis and release of thyroid hormones will be increased so that thyroid hormone secretion does not become too low. The principle of this action of iodine is not known.
(iv) Role of sympathetic nerves
The thyroid follicle is innervated by sympathetic nerves, and electrical stimulation of sympathetic nerves can increase thyroid hormone synthesis
Examination of the thyroid gland
(a) Visual examination
The size and symmetry of the thyroid gland are observed. In normal people, the thyroid gland is not prominent in appearance, but in women it may increase slightly during puberty. If it is not easy to identify the thyroid gland, the patient should be instructed to put both hands behind the pillow and tilt the head back, and then observe it.
(B) Palpation
(1) Thyroid isthmus: The thyroid isthmus is located in front of the second to fourth tracheal rings below the cricoid cartilage. The soft tissue in front of the trachea can be felt by touching it with the thumb in front of the subject or with the finger behind the subject from the upper sternal notch upwards to determine whether there is thickening.
(2) Lateral thyroid lobe: frontal palpation: one thumb applies pressure to the thyroid cartilage on one side, pushing the trachea to the opposite side, the other hand shows the finger and middle finger pushing the lateral thyroid lobe forward at the posterior edge of the sternocleidomastoid muscle on the opposite side, the thumb palpates at the anterior edge of the sternocleidomastoid muscle, with swallowing action, repeat the examination, the pushed thyroid gland can be palpated. Use the same method to examine the other side of the thyroid. Posterior palpation: similar to the anterior palpation. The thumb of one hand applies pressure to the thyroid cartilage on one side, pushing the trachea to the opposite side. The thumb of the other hand pushes the thyroid gland forward at the posterior edge of the sternocleidomastoid muscle on the opposite side, and the thyroid gland is palpated by the thumb and middle finger at its anterior edge. Repeat the examination with the swallowing motion. Use the same method to examine the other side of the thyroid gland.
(iii) Auscultation
When an enlarged thyroid gland is palpated, a bell-shaped stethoscope placed directly on the enlarged thyroid gland can be helpful in diagnosing hyperthyroidism if a low-pitched continuous venous “buzzing” sound is heard. In addition, a systolic arterial murmur may be heard in diffuse goiter with hyperfunction.
(D) The enlarged thyroid gland can be divided into three degrees: degree I if the enlargement is not visible but palpable; degree II if the enlargement is visible and palpable but within the sternocleidomastoid muscle; and degree III if it exceeds the outer edge of the sternocleidomastoid muscle.
Thyroid surgery
Thyroid surgery is an effective treatment for hyperthyroidism and complications are rare, especially when performed in hospitals with high medical standards. Therefore, patients who need surgery for hyperthyroidism should not worry too much about the complications that are unlikely to occur, or else they will be too concerned about the surgical treatment. As a result, the opportunity to cure the disease is lost.
The complications of several major surgical procedures are as follows.
(1) Bleeding: Intraoperative ligation that is not tight and falls off can cause postoperative bleeding. Arterial bleeding is rapid and develops quickly, and often requires reoperation to stop the bleeding. Venous hill hemorrhage develops more slowly and does not necessarily require reoperation to stop the hemorrhage.
(2) Recurrent laryngeal nerve palsy: surgical injury to the recurrent laryngeal nerve can cause recurrent laryngeal nerve palsy. Unilateral injury can cause voice changes, and injury to both sides can cause respiratory distress.
(3) Supraglottic nerve palsy: injury to the supraglottic nerve can cause relaxation of the vocal cords and change in tone.
(4) Hypocalcemic convulsions: Removal or injury to the parathyroid glands (long on the dorsal side of the thyroid gland, usually 4 parathyroid glands) can cause hypocalcemic convulsions, showing characteristic twitching of the hands and feet.
(5) Hyperthyroid crisis: surgery induced hyperthyroid crisis.
(6) Hypothyroidism: A small number of patients develop hypothyroidism after surgery. There are two possible reasons for the occurrence of hypothyroidism. One, too much thyroid gland has been removed, leaving behind thyroid tissue that cannot synthesize and secrete enough thyroid hormone. Second, in cases of chronic lymphatic thyroiditis, antibodies that destroy the thyroid tissue are present in the body, so hypothyroidism can occur even if not too much thyroid tissue is removed. Hypothyroidism can occur early or late, but in general, if it occurs early, it may be due to excessive thyroid removal; if it occurs late, it may be associated with chronic lymphatic thyroiditis.
Dietary contraindications for patients with thyroid disorders
Hyperthyroidism
Hyperthyroidism is not caused by iodine deficiency, so iodine treatment should be based on the precise dosage of iodine as directed by a physician. Otherwise, a large amount of iodine in the diet, such as kelp, seaweed, kombu, etc., will affect the doctor’s judgment and analysis of the disease and will interfere with clinical treatment.
2.Patients with hyperthyroidism are mostly Yin deficiency and Yang hyperactivity, so the following foods should be avoided Avoid spicy foods, such as chili, leek, raw onion, ginger, garlic, etc., as well as foods that are hot and have aphrodisiac effects, such as cinnamon, ginger, mutton, dog meat, venison, sparrow, sea shrimp, seahorse, sea cucumber, etc. Avoid frying, deep-frying, burning, baking food, so as not to help heat Yang, dry Yin consumption. Do not eat greasy and thick food, so as not to help dampness and phlegm heat.
3, prohibit smoking and alcohol, tobacco and alcohol are pungent, dry and fiery things, long hurt Yin, dryness, heat. Often aggravate the condition and interfere with treatment.
Hypothyroidism
1, hypothyroidism, Chinese medicine identifies Yang deficiency as the main aspect, Yang deficiency will produce internal cold. Therefore, the diet should be warm yang to supplement the deficiency food, avoid eating too much cold, such as ice cream, popsicles, ice water, chilled food, etc..
2, hypothyroidism, mostly combined with elevated serum cholesterol, should properly regulate the intake of lipids.