hypothyroidism



Overview

An endocrine disorder in which insufficient thyroid hormone or thyroid hormone resistance leads to hypometabolism of the body with symptoms such as chills, fatigue, low sweating, weight gain, memory loss, constipation, etc. Associated with autoimmunity, medications, and surgeries mainly through thyroid hormone replacement therapy

Definition

Hypothyroidism, abbreviated as hypothyroidism, is a generalized hypometabolic syndrome caused by insufficient synthesis or secretion of thyroid hormone leading to hypothyroidism, or thyroid hormone resistance.

Types

Classification according to the location of the lesion

Primary hypothyroidism, central hypothyroidism and thyroid hormone resistance syndrome.

Primary hypothyroidism

Primary hypothyroidism is the most common form of hypothyroidism, also called thyroid hypothyroidism, which is caused by lesions of the thyroid gland itself.

For example, it is caused by thyroid autoimmune disease, thyroid surgery and radioactive iodine treatment for hyperthyroidism.

Central hypothyroidism

Less common, including pituitary or hypothalamic hypothyroidism. It is often caused by hypothalamic and pituitary tumors, radiation therapy, surgery, and ischemic necrosis of the pituitary gland in postpartum hemorrhage.

Hypothyroidism caused by the hypothalamus, also called triple-onset hypothyroidism, is rare and can be seen in hypothalamic syndromes, hypothalamic tumors, inflammation, and radiation therapy.

Thyroid hormone resistance syndrome

It is an autosomal dominant disorder.

It is a syndrome caused by the insensitivity of peripheral tissues to thyroid hormone and the inability of thyroid hormone to exert its normal biological effects.

Classification by cause

It can be classified as autoimmune hypothyroidism, drug-induced hypothyroidism, hypothyroidism after thyroid surgery, hypothyroidism after radioactive iodine therapy, hypothyroidism after insufficient iodine intake, idiopathic hypothyroidism, hypothyroidism after surgery for pituitary gland or hypothalamus tumors, congenital hypothyroidism, and consumptive hypothyroidism.

Classification according to severity

According to the thyroid function test can be divided into clinical hypothyroidism and subclinical hypothyroidism, mucous edema coma.

Classification according to the age of occurrence

It can be classified into adult-type hypothyroidism, juvenile-type hypothyroidism and neonatal hypothyroidism.

Morbidity

The prevalence of hypothyroidism varies widely and is related to factors such as etiology, diagnostic criteria, gender, age, and race.

The prevalence of hypothyroidism in adult women is higher than that in men, and the prevalence increases with age.

The prevalence of subclinical hypothyroidism in China is 16.7%, and the prevalence of clinical hypothyroidism is 1.1%.

Causes

Causes

Autoimmune thyroiditis

Antibodies attack the thyroid tissue and cause hypothyroidism, such as Hashimoto’s thyroiditis and atrophic thyroiditis.

Treatment-induced hypothyroidism

Thyroid surgery, radioactive iodine treatment of the thyroid gland, radiotherapy to the neck, etc., leading to hypothyroidism caused by excessive destruction of the thyroid gland.

Medications that affect the thyroid gland

Taking lithium carbonate, amiodarone, sodium para-aminosalicylate, potassium perchlorate, prednisone, thiocyanate, tyrosine kinase inhibitors, thioureas, sulfonamides, etc.

Pituitary or hypothalamic disease

It is caused by the hypothalamus and pituitary gland’s secretion of thyrotropin-releasing hormone or reduced synthesis and secretion of thyrotropin. It can be seen in pituitary tumor, pituitary inflammation, pituitary ischemic necrosis, hypothalamic tumor, chronic inflammation of the hypothalamus and so on.

Iodine overdose or iodine deficiency

Excess iodine can cause hypothyroidism in people with underlying thyroid disease (e.g., Hashimoto’s thyroiditis), and can also induce and exacerbate autoimmune thyroiditis. Iodine deficiency can cause iodine-deficiency endemic goiter.

Congenital hypothyroidism

This is characterized by an abnormality in the genes involved in thyroid hormone synthesis, such as an absent or ectopic thyroid gland.

Transient hypothyroidism

There are subacute thyroiditis, painless thyroiditis, and postpartum thyroiditis.

Others

Depletion hypothyroidism, thyroid hormone resistance syndrome, etc.

Pathogenesis

Hypothyroidism is caused by insufficient synthesis or secretion of thyroid hormones, or diminished action of thyroid hormones by surrounding tissues.

Thyroid hormone is secreted by the thyroid gland, and thyroid hormone is essential for maintaining normal metabolism and promoting growth and development.

People at risk

Anyone can develop hypothyroidism, but the following groups of people are at relatively high risk of developing hypothyroidism.

People with autoimmune diseases.

First-degree relatives with a history of thyroid disease.

People with a history of radioactive iodine treatment of the thyroid gland.

People who have had thyroid surgery.

People who have taken medications such as lithium carbonate, amiodarone, sodium para-aminosalicylate, and potassium perchlorate.

People who live in iodine-deficient areas and do not take iodized salt supplements.

People with pituitary or hypothalamic disorders.

People who have hyperprolactinemia.

People who suffer from postpartum thyroiditis.

Symptoms

Depending on the age of onset, hypothyroidism is categorized as neonatal hypothyroidism, juvenile hypothyroidism, and adult hypothyroidism. In adults, hypothyroidism often has an insidious onset and progresses slowly, with typical symptoms appearing months or even years later. Early symptoms of hypothyroidism are variable and lack specificity.

Neonatal hypothyroidism

Also known as cretinism, neonatal hypothyroidism is not obvious, and the following symptoms may appear a few weeks after birth.

Dry, thick, pale or yellowish skin with wrinkles on the forehead.

A short nose with a flattened bridge and an upturned tip.

Lips are thick, often open, and drool easily.

The tongue is large and protrudes outward.

Short limbs and short stature.

Low body temperature.

Growth and development are significantly behind peers, and adults are often short.

Poor response to the outside world.

There may also be goiter, permanent intellectual, hearing and speech disorders.

Juvenile-type hypothyroidism

The developmental backwardness and change in appearance of young children are not as obvious as those with cretinism, but the others are similar to those with cretinism.

At the same time, there are different degrees of growth retardation and delayed puberty.

Adult-onset hypothyroidism

Mild type is characterized by mild or atypical symptoms; severe type affects a wide range of systems and is called mucous edema.

Early symptoms

The earliest symptoms of adult-onset hypothyroidism are decreased sweating, fear of cold, slow movements, depression, fatigue, drowsiness, mental retardation, poor appetite, weight gain, and constipation.

Typical symptoms

Hypometabolic symptoms

Fatigue, slow movements, lethargy, memory loss and poor concentration, chills and lack of sweating.

Mucous edema face

Dull expression, facial edema, thickened nose and lips.

Skin

Dry, thick, pale or waxy skin, low body temperature, thinning and dry hair, loss of eyebrows.

Mental Nervous System

Mental depression and unresponsiveness with tinnitus and dizziness; in severe cases, there may be rigidity, dementia, and lethargy.

Muscles and bones

Weakness (especially in the shoulders and back), swollen and painful muscle joints.

Digestive system

Loss of appetite, bloating, constipation.

Cardiovascular system

May have bradycardia.

Respiratory system

Obstructive sleep apnea (snoring with apnea, high and low snoring that can be interrupted and severe suffocation).

Other

Swelling sensation in hands and feet, muffled pronunciation; impotence and loss of libido in men; excessive menstruation and infertility in women.

Complications

Untreated hypothyroidism can cause a variety of complications.

Goiter

Hormonal stimulation of the thyroid gland in the early stages causes the gland to enlarge, and severe goiter may interfere with swallowing or breathing. In later stages, most of the thyroid gland shrinks and becomes smaller.

Heart disease

Involvement of the heart may result in pericardial effusion and heart failure. Long-term illnesses are prone to complications of atherosclerosis and coronary heart disease, angina pectoris and arrhythmia.

Mental health problems

Depression may occur early in hypothyroidism and may become more severe over time.

Peripheral neuropathy

Long-term uncontrolled hypothyroidism can damage peripheral nerves (the nerves that carry messages from the brain and spinal cord to the rest of the body). Peripheral neuropathy may cause pain, numbness and tingling sensations in the affected area.

Mucous edema coma

Most often seen in the elderly or in people who have been untreated for a long time and is easily triggered by cold.

Common triggers include cold, infection, surgery, severe physical illness, interruption of thyroid hormone therapy, use of anesthesia, and sedative medications.

Clinical manifestations include drowsiness, hypothermia (body temperature <35℃), slowed respiration, bradycardia, decreased blood pressure, muscle relaxation of limbs, weakened or disappeared reflexes, or even coma and shock, and in severe cases, the patient’s life can be jeopardized by respiratory depression.

Infertility

Low levels of thyroid hormones can interfere with ovulation, thus affecting fertility. In addition, certain causes of hypothyroidism (e.g. autoimmune diseases) can impair fertility.

Birth defects

Babies born to women with untreated hypothyroidism may have a higher risk of birth defects than babies born to healthy mothers, and these children are also more likely to have serious intellectual and developmental problems.

Seeking Medical Treatment

Department of Medicine

Endocrinology

When you feel tired for no apparent reason, or have low metabolic symptoms such as chills, decreased sweating, or depression, it is advisable to seek prompt medical attention.

Emergency Department

When symptoms such as lowered body temperature, slowed respiration, bradycardia, coma, etc. occur, immediate consultation is recommended.

Preparation for medical treatment

Preparation for medical consultation: registration, preparation of documents, common problems

Tips for the doctor

In order to facilitate the doctor’s examination, try not to wear high-collared clothes or necklace jewelry.

If there is any weight change, it is recommended to record the time and result of weight measurement for the doctor’s reference.

Preparation Checklist for Doctor’s Visit

Are there any chills, fatigue, decreased sweating, constipation, poor concentration?

How long have the above symptoms lasted?

Has there been any change in weight in the last six months?

Does any blood relative have thyroid disease?

Are there any allergies to drugs, food or other substances?

Are there any diseases such as high blood pressure, diabetes, systemic lupus erythematosus, rheumatoid arthritis, etc.?

Has anyone had thyroid surgery or received thyroid iodine-131 treatment?

Laboratory tests: thyroid function, thyroid autoantibodies, blood test, liver function, kidney function.

Imaging tests: thyroid ultrasound, thyroid radionuclide scan, cardiac ultrasound, pituitary magnetic resonance imaging

Other tests: electrocardiogram

Thyroid hormone: levothyroxine sodium tablets

Imidazoles: methimazole, carbimazole

Thiouracil: propylthiouracil

Iodine-containing drugs: amiodarone, compound iodine solution, iodine-containing contrast media

Glucocorticoids: hydrocortisone, prednisone acetate, methylprednisolone, dexamethasone

Diagnosis

Diagnosis is based on

Medical history

At the initial visit, a detailed medical history will help the doctor diagnose hypothyroidism.

Past history

History of previous thyroid disorders or treatments, such as history of autoimmune disorders, history of thyroid surgery, history of radioactive iodine treatment to the neck, history of pituitary disorders, history of postpartum hemorrhage in women, etc.

History of drug application

Lithium carbonate, amiodarone, sodium para-aminosalicylate, potassium perchlorate, prednisone, thiocyanate, tyrosine kinase inhibitors, thioureas, sulfonamides, etc.

Dietary habits

Consumption of iodized salt, long term consumption of large amounts of cabbage, nori, kale, cassava, etc.

Family history

History of autoimmune thyroid disease in first-degree relatives (father, mother, siblings) or second-degree relatives (grandfather, grandmother, grandparents, uncles, aunts).

Clinical manifestations

Symptoms.

Typical patients may have hypometabolic symptoms, such as chills, fatigue, feeling of swelling in hands and feet, drowsiness, memory loss, and less sweating, as well as joint pain, weight gain, constipation, menstrual disorders in females, or excessive menstruation, and infertility.

Physical Examination

Hypothyroidism

The face is swollen, dull and apathetic.

Pale face, thick lips, and teeth marks are visible around the tongue.

Thinning and loss of outer 1/3 of eyebrows and thinning of male beard.

Skin

Dry skin, decreased skin temperature, skin of the palms of the hands and feet may appear ginger-colored.

Hair is sparse and dry, and mucous edema may be present anteriorly on the tibiae of both lower extremities, with no depression on pressure.

Nervous system: prolonged relaxation period of Achilles tendon reflex.

Cardiovascular system: bradycardia, diminished heart sounds, and enlarged heart boundaries.

Digestive system: weakened bowel sounds, drumming sounds on abdominal percussion, paralytic bowel obstruction in some people.

Laboratory tests

Thyroid function tests

The main tests include: serum thyroid stimulating hormone (TSH), total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3), free triiodothyronine (FT3).

Primary clinical hypothyroidism may have increased serum TSH, decreased FT4, and in severe cases, decreased FT3. Primary subclinical hypothyroidism has increased serum TSH and normal TT4 and FT4. Central hypothyroidism has normal or decreased serum TSH and decreased FT4 and TT4.

Thyroid autoantibodies

Thyroid autoantibodies, including thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb), are the main indicators for determining the cause of primary hypothyroidism and diagnosing autoimmune thyroiditis (including Hashimoto’s thyroiditis and atrophic thyroiditis).

Significantly elevated TPOAb and TgAb suggest that hypothyroidism is caused by autoimmune thyroiditis.

Other auxiliary tests

Cardiac function tests

Including electrocardiogram, ultrasound examination, etc., can understand whether there is any abnormality in cardiac function and whether there is pericardial effusion.

X-ray examination

Bone age phase to know the bone age, bone and joint phase to know whether there is any abnormality of ossification.

Thyroid imaging

Including thyroid nuclear imaging, thyroid tomography examination, magnetic resonance examination, etc., which can help diagnosis and differential diagnosis.

Differential diagnosis

Similarities: Reduced T3 is seen on thyroid function tests.

Differences: Low T3 syndrome is not caused by thyroid disease, but by the body’s adaptive response to illness in the setting of severe chronic, wasting systemic disease. It can be seen in malnutrition, anorexia nervosa, diabetes mellitus, and liver disease. It can be identified by thyroid function tests, which may show decreased serum TT3 and FT3 levels, increased reverse T3 (rT3) levels, and normal or mildly elevated TSH levels. The severity of the disease is related to the degree of T3 reduction.

Chronic nephritis and nephrotic syndrome

Similarities: Edema is also present.

Differences: In chronic nephritis and nephrotic syndrome, there may be abnormalities in renal function tests, while thyroid function tests are usually not abnormal.

Pituitary prolactinoma

Similarity: Primary hypothyroidism sometimes presents with manifestations similar to those of pituitary prolactinoma, such as pituitary reactive hyperplasia, hyperprolactinemia, and breast milk overflow.

Differences: Pituitary prolactinoma can be differentiated by thyroid function tests and pituitary magnetic resonance examination, which shows pituitary space-occupying lesions.

Primary Hypoadrenocorticism

Similarities: Clinical manifestations such as fatigue and indifference may also be present.

Differences: Primary hypoadrenocorticism can be differentiated by plasma cortisol and plasma adrenocorticotropic hormone (ACTH), and primary hypoadrenocorticism is characterized by a marked increase in plasma basal ACTH.

Anemia

Similarity: 25% to 30% of patients with hypothyroidism have anemia. Women with hypothyroidism may have excessive menstruation, which can cause anemia.

Differences: Thyroid function is usually not abnormal in anemic patients.

Depression

Similarity: Symptoms of hypothyroidism in the elderly are atypical and can be easily confused with depression. Symptoms such as chills, sluggishness, loss of appetite, depressed mood, poor sleep and depression may be present.

Differences: Patients with depression usually do not have abnormal thyroid function.

Pericardial effusion

Similarities: Hypothyroidism can also cause pericardial effusion, which needs to be differentiated from pericardial effusion caused by other diseases.

Difference: Pericardial effusion can be differentiated from other causes of pericardial effusion by measuring thyroid function and by electrocardiography and hemodynamics.

Treatment

Treatment objectives

Signs and symptoms of primary hypothyroidism disappear and TSH, FT4, TT4 reach normal range.

Secondary hypothyroidism FT4, TT4 reach normal range.

General treatment

Pay attention to rest: avoid overwork and stress.

Enhance warmth: adjust the room temperature between 22～23℃, pay attention to keep warm and prevent cold.

Regulate diet: Eat high protein, high vitamin, low sodium, low fat diet, chew slowly, small and frequent meals.

Others: iodine deficiency should be supplemented with iodine; anemia should be supplemented with iron, vitamin B12 and folic acid.

Hormone replacement therapy

Drugs: Mainly supplement levothyroxine (L-T4), which usually requires lifelong medication.

Precautions: the elderly and people with heart disease should start with a small dose of the drug and gradually increase the dose; do not stop taking the drug arbitrarily.

Dosing time: take 30-60 minutes before breakfast or before bedtime, once a day.

Adverse reactions: Elderly patients and patients with coronary heart disease may experience palpitations and even angina attacks after taking the drug, note that the starting dose should be small, followed by slow dosage. Overdose may have increased appetite, insomnia, palpitation, irritability, trembling, diarrhea and other drug hyperthyroidism hypermetabolic manifestations.

Influence on drug absorption: aluminum hydroxide, calcium carbonate, calamine, aluminum sulfate, ferrous sulfate, sodium phenytoin, carbamazepine, rifampicin, amiodarone and other drugs will affect the absorption of levothyroxine, so it should be taken at intervals of more than 4 hours.

Traditional Chinese Medicine (TCM)

Hypothyroidism is similar to “gall labor” in Chinese medicine, which can be categorized as “deficiency labor”, “gall disease” and “edema”. The first is the “galls” in Chinese medicine. It is due to congenital insufficiency, acquired long illness disorder, deficiency of organs and qi, positive deficiency and evil caused.

Chinese medicine treatment of hypothyroidism, the need to identify evidence-based treatment, it is recommended that the regular medical institutions to avoid superstitious local remedies, partial prescriptions, secret prescriptions. The following formulas and proprietary Chinese medicines are available for treating hypothyroidism.

Formulas: Sijunzi Tang combined with Dazhongyuan Decoction plus or minus, Lizhong Pill combined with Pilio Pill plus or minus, Zhenwu Tang combined with Linggui Juguan Tang plus or minus, Jin Gui Ren Qi Pill plus or minus, and so on.

Chinese patent medicines: Jin Gui Kidney Qi Pill, Zhong Yi Qi Pill, Radix Rehmanniae Pill.

Treatment of Critical Illness

Mainly the treatment of mucous edema coma.

Supplementation of thyroid hormone: oral levothyroxine sodium replacement therapy is preferred, for those who have difficulty in oral intake, the drug can be given from the gastric tube, and intravenous injection can be used if possible, and then changed to oral intake after waking up.

Keep the airway open: oxygen, tracheotomy and mechanical ventilation if necessary.

Other: remove triggers, keep warm, intravenous hydrocortisone, symptomatic supportive therapy, infection control.

Prognosis

Cure

After appropriate treatment, the symptoms and signs of hypothyroidism can be relieved and improved to varying degrees, and normal life and work can be resumed, but most patients need to take medication for life.

After standardized treatment, women of childbearing age with hypothyroidism can get pregnant and deliver healthy babies.

If treatment is started within 3 months after birth, the prognosis of infants and young children with hypothyroidism is still good, and most of them can reach normal IQ; if the diagnosis is not made early and the treatment is started after 6 months, although thyroxine can improve the growth condition, the IQ will still be seriously impaired.

Harmful

Thyroid hormone is an important hormone in the body, and hypothyroidism affects multiple systems throughout the body.

It can cause low metabolic symptoms, which may include fatigue, weight gain, and slowness of movement, as well as affecting the nervous system in the form of memory and concentration loss, which can have a serious impact on the patient’s quality of life.

Primary hypothyroidism can also lead to hypothyroid heart disease, with heart enlargement and pericardial effusion.

Untreated hypothyroidism in infancy can lead to stunted growth and irreversible severe damage to IQ, and untreated hypothyroidism in early childhood can cause irreversible damage to the physical and intellectual abilities of the affected child.

In adult women, severe hypothyroidism can be accompanied by decreased libido and ovulation disorders, menstrual cycle disorders and increased menstrual flow, and infertility.

In men, hypothyroidism can lead to loss of libido, impotence and reduced spermatozoa, which may affect fertility to a certain extent.

Untreated hypothyroidism may also be complicated by mucous edema, coma, shock, etc., and may even be life-threatening.

Untreated hypothyroidism during pregnancy has adverse effects on both the mother and the fetus, including spontaneous abortion, preterm delivery, preeclampsia, gestational hypertension, postpartum hemorrhage, low birth weight babies, stillbirth, and impaired fetal intellectual and motor function.

If left untreated, the patient’s condition will progressively worsen and can lead to death due to complications of heart disease or mucous edema coma. The prognosis of mucous edema coma is poor and the mortality rate is as high as 70%.

Daily

Life management

Dietary management

Dietary principles

The proportion of the three major nutrients in the diet should be balanced, with high-quality protein as the main ingredient, and protein should be 1 gram per kilogram of body weight. Fat and carbohydrates should not be too high, and the intake should not exceed 30% and 55%-65% of the total energy respectively.

Supplementary iodine and calcium-rich foods.

Dietary fiber and vitamins should be rich, daily food vegetables not less than 500 grams, fruit not less than 200 grams.

Limit the consumption of animal fats and oils, not more than 30 grams of cooking oil per day; limit the consumption of foods that cause goiter.

Those with mucous edema should limit salt intake to no more than 3 grams per day.

Hypothyroid patients with gastrointestinal symptoms should avoid eating raw and cold foods and focus on warm foods.

Reasonable choice of food

Eat iodine-rich foods regularly, such as kelp, seaweed and seaweed, and use iodized salt when cooking. Hypothyroidism caused by autoimmune diseases requires less iodine-containing food.

Regularly consume calcium-rich foods such as milk and soy products and shrimp skin.

Limit foods that can cause goiter including kale, green cauliflower, mustard leaves, and spinach, but these foods can be eaten cooked and avoided with dips.

Limit high-fat foods such as oil (which should be limited), peanuts, walnuts, sesame seed paste, ham, pancetta, and cheese.

Avoid foods rich in high cholesterol, such as cream, animal brains and offal.

Anemia can be prevented by regular consumption of iron-rich foods, such as pig’s blood.

Exercise Management

Perform moderate exercise such as walking, brisk walking, etc. for 30 minutes 3 to 5 times a week.

Lifestyle

Regular work and rest, avoid staying up late and straining.

Establish a normal bowel pattern, have regular bowel movements every day, and develop the habit of regular bowel movements.

Pay attention to personal hygiene, prevent infection and trauma.

Pay attention to keep warm, especially in winter, to avoid the cold.

Face the disease with a positive mindset, avoid fear, anxiety and other bad emotions.

Review

At the initial stage of treatment, hypothyroidism and subclinical hypothyroidism should check the thyroid function every 4 to 8 weeks, and review at least every 6 to 12 months after the treatment reaches the standard.

For hypothyroidism during pregnancy and subclinical hypothyroidism during pregnancy, thyroid function should be checked every 2 to 4 weeks during the first half of pregnancy, and after the status is stabilized, it should be extended to every 4 to 6 weeks, and thyroid function should be rechecked 6 weeks after delivery.

Symptoms such as palpitations, insomnia, irritability and trembling should be consulted and drug dosage should be adjusted.

If drowsiness, body temperature <35℃, slow respiration, hypotension, bradycardia, etc. occur, consult a doctor promptly.

Medication management

Use hypnotic, sedative, analgesic, anesthesia and other drugs with caution and must be administered under medical supervision.

Patients with primary hypothyroidism need to take medication for life and on time.

Prevention

Patients without thyroid autoimmune disease should insist on iodized salt, and pregnant and breastfeeding women in particular need to be supplied with adequate iodide.

Patients with thyroid autoimmune disease should avoid eating large quantities of high iodine foods such as kelp and nori for a long period of time; use iodine-containing drugs reasonably under the guidance of doctors.

Adult hyperthyroidism should be treated with antithyroid drugs strictly according to the doctor’s prescription, paying attention to the dosage and duration of treatment and adjusting them according to the condition at any time.

Pregnant women should have regular physical examination, early detection of fetal hypothyroidism and early intrauterine or postnatal treatment will significantly reduce the incidence of congenital hypothyroidism in newborns and improve their poor prognosis.

After thyroidectomy, the patient should take medication for lifelong replacement therapy, follow the doctor’s instructions and undergo regular checkups.