Thyroid disorders are divided into two main categories: thyroid disorders treated medically and thyroid disorders treated surgically. Internally treated thyroid disorders include hyperthyroidism (commonly known as hyperthyroidism) and inflammatory thyroid disorders (including acute, subacute and chronic inflammatory thyroid disorders). Surgical treatment of thyroid disorders includes goiter and thyroid tumors. The main difference between the two is that thyroid diseases treated medically have abnormal thyroid function tests, while thyroid diseases treated surgically have normal thyroid function tests. However, the two are not absolutely isolated from each other, and they can be transformed into each other, especially in the case of medical thyroid disease that may also require surgical treatment. This article introduces four types of thyroid disorders: goiter, hyperthyroidism (hyperthyroidism), inflammation of the thyroid gland, and thyroid tumors.
I. Goiter
Goiter is divided into two categories: simple goiter and nodular goiter.
Simple goiter
The cause of simple goiter is related to iodine deficiency in the diet (e.g. mountainous areas) and increased iodine demand under certain conditions (e.g. pregnancy, growth spurt).
In patients with simple goiter, an enlarged thyroid gland can usually be found in the neck and an ultrasound can confirm an enlarged thyroid gland without nodules in the thyroid gland. Patients with simple goiter have normal thyroid function, which can be distinguished from hyperthyroidism and Hashimoto’s thyroiditis.
Patients with simple goiter do not require surgery, but only supplemental thyroxine preparations. The enlarged thyroid gland will usually subside on its own after a period of medication. At present, there are two main types of thyroxine preparations used in China, one is thyroxine tablets, 40mg/capsule, and the other is levothyroxine nano-tablets (such as eugenol and retix), 50ug/capsule or 100ug/capsule. Thyroxine tablets are animal preparations extracted from the thyroid gland of pigs, which are crude and not very pure; levothyroxine tablets are synthetic preparations, which are more pure.
Nodular goiter
It is the most common type of thyroid disease. Its cause is not well understood and may be related to endocrine disorders, high iodine diet, environmental factors, genetic factors and history of radiation exposure.
Patients with nodular goiter usually present to the doctor through physical examination or find a lump in the neck on their own. On examination, nodules of more than 1 cm can be felt, mostly soft or tough, with a smooth surface and clear borders, and can move up and down with swallowing. The thyroid function tests are within the normal range, and ultrasound examination indicates that the thyroid gland is normal or enlarged, with single or multiple nodules in one or both glands. These nodules may be cystic, mixed, or parenchymal; they may be oval in shape. The nodules may be surrounded by an acoustic halo. The shape may be irregular; the borders may or may not be well defined; the blood supply may or may not be abundant; and the parenchymal nodules may present with posterior coarse calcifications with acoustic shadowing, but not usually with microcalcifications.
The only cure for a nodular goiter is surgery, but not all nodular goiters require surgical treatment. Surgery is usually considered in nodular goiter with nodules at least more than 20 mm or if malignancy is suspected or if pressure is present or if it is located behind the sternum or secondary to hyperthyroidism or if it affects aesthetics, work and life. If none of these conditions are present, ultrasound follow-up at six-month intervals is recommended. Drugs are not effective in treating nodular goiter.
II. Hyperthyroidism
It is mostly seen in young and middle-aged women. The clinical manifestations are mainly caused by excessive circulating thyroid hormones. The symptoms are agitation, irritability and insomnia, palpitations, fatigue, fear of heat, excessive sweating, weight loss, hyperphagia, increased stool frequency or diarrhea, and scanty menstruation in women. On physical examination, most patients have goiter of varying degrees, which is diffuse, of medium texture, and without pressure pain. Some patients have proptosis.
Thyroid function tests have increased blood T3, T4, FT3, FT4 and decreased TSH (generally <0.1mIU/L). Ultrasound examination indicates diffuse enlargement of the thyroid gland with increased blood supply; nodules may be found in the thyroid gland in some patients.
General treatment of hyperthyroidism includes rest, adequate calories and nutrition. There are three main types of treatment for hyperthyroidism: 1. Anti-thyroid drugs (ATD). The main drugs are methimazole (MMI) and propylthiouracil (PTU). The side effects of anti-thyroid drugs are rash, skin pruritus, leukopenia, granulocytopenia, toxic liver disease, etc. 2. 131 iodine therapy. Indications include: adult Graves’ hyperthyroidism with goiter II or higher; failure of ATD therapy or allergy; recurrence of hyperthyroidism after surgery; hyperthyroid heart disease or hyperthyroidism with other causes of heart disease; hyperthyroidism combined with leukopenia and/or thrombocytopenia or pancytopenia; hyperthyroidism in the elderly; hyperthyroidism with diabetes mellitus; toxic multinodular goiter; autonomous functional thyroid nodules combined with hyperthyroidism. The main complication after 131I treatment of hyperthyroidism is hypothyroidism. After the onset of hypothyroidism, replacement therapy with thyroxine preparations can be used to maintain normal thyroid function. 3. Surgery. The indications for surgery are moderate or severe hyperthyroidism with ineffective long-term medication or poor results; relapse after stopping medication with a large thyroid gland; nodular goiter with hyperthyroidism; compression of surrounding organs or retrosternal goiter; suspected coexistence with thyroid cancer; children with poor results of hyperthyroidism treated with antithyroid medication; and those with poor control of hyperthyroidism medication during pregnancy, which can be performed in the middle of pregnancy (13th-24th weeks) surgical treatment.
Inflammatory thyroid disease
Subacute thyroiditis
Subacute thyroiditis is often secondary to upper respiratory tract infection and tends to occur more frequently in spring and fall. Most cases of subacute thyroiditis occur in women aged 40-50 years and are characterized by neck pain, tenderness in one side of the thyroid gland, fever, joint pain, and other systemic inflammatory reactions. Some patients may develop hyperthyroidism. Most patients have a hard and swollen thyroid gland with pressure pain.
The patient’s blood sedimentation is increased, blood FT3 and FT4 are normal or mildly increased, TSH is normal or mildly decreased, and serum TPOAb is often transiently increased. ultrasound may reveal an enlarged thyroid gland, with hypoechoic or heterogeneous focal areas within the gland, with poorly defined borders and irregular morphology, and may have limited calcification foci.
Subacute thyroiditis is a self-limiting inflammatory disease that usually resolves on its own without specific treatment. However, patients should rest properly and may be given prednisone or anti-inflammatory and analgesic drugs to reduce symptoms.
Chronic lymphocytic thyroiditis
Also known as Hashimoto’s thyroiditis. It is most commonly seen in women, with a prevalence of 30-60 years old. Most patients have no neck discomfort, but a small number of patients have localized pressure and vague neck pain. On physical examination, the thyroid gland is usually bilaterally and symmetrically enlarged, and the isthmus is also enlarged at the same time. The texture is firm and the surface is smooth or nodular. A small number of patients may have enlarged lymph nodes in the neck, but they are soft.
In the early stage of the disease, blood T3, T4, FT3, FT4 and TSH are generally normal, but as the disease progresses, TSH gradually increases, and finally T3, T4, FT3 and FT4 gradually decrease, resulting in hypothyroidism. The thyroglobulin antibody (TGAb) or thyroid peroxidase antibody (TPOAb) is always increased. ultrasound reveals diffuse enlargement or nodular enlargement of the thyroid gland with uneven echogenicity and lattice-like or sheet-like echogenic changes. The blood supply to the gland is generally rich.
Treatment for chronic lymphocytic thyroiditis is more limited. If the thyroid gland is significantly enlarged or if hypothyroidism is present it can be treated with thyroxine preparations. Selenium has now been found to be somewhat effective in the treatment of chronic lymphocytic thyroiditis, so selenium yeast tablets can also be taken for this purpose.
If chronic lymphocytic thyroiditis causes enlargement of the thyroid gland with symptoms of pressure or nodules in the thyroid gland with high suspicion of malignancy, surgical treatment should be considered.
Thyroid tumors
Benign tumors of the thyroid gland
Benign tumors of the thyroid gland are mainly thyroid adenomas. Most of them occur in young adults. The clinical manifestation is mostly a lump in front of the neck, with slow growth and no conscious symptoms. On physical examination, the surface of the mass is smooth, soft or tough, with clear borders, and can move up and down with swallowing. If there is bleeding in the adenoma, the lump may increase rapidly with local pain, and these symptoms usually disappear within 1-2 weeks.
The thyroid function tests are generally within the normal range, but if it is a high-functioning adenoma, T3, T4, FT3, FT4 may be increased, and TSH may be decreased; ultrasound examination of the thyroid gland is usually a single nodule, but it may be multiple; it is substantial or mixed, mostly oval, with clear borders and regular shape, and there may be an acoustic halo around it, and the blood supply may be abundant.
Generally, thyroid adenomas under 10 mm in diameter are recommended to be observed and followed up by ultrasound regularly. Surgery may be considered if the adenoma has recently increased rapidly, if there are symptoms of pressure, if there is a tendency of malignancy during follow-up, or if it is diagnosed as a high-functioning adenoma.
Malignant thyroid tumor
It can be divided into differentiated thyroid cancer including papillary thyroid cancer and follicular thyroid cancer, and low differentiated thyroid cancer such as medullary carcinoma and undifferentiated thyroid cancer. Currently, the incidence of thyroid cancer is increasing year by year.
The cause of thyroid cancer is not very clear, but may be related to dietary factors (high iodine or iodine deficiency diet), history of exposure to radiation, increased estrogen secretion, genetic factors, or other benign thyroid diseases such as nodular goiter, hyperthyroidism, thyroid adenoma and especially chronic lymphocytic thyroiditis.
Differentiated thyroid cancer is more common in females and is commonly seen between the ages of 30-60. Differentiated thyroid cancer develops slowly. Patients may find a painless lump in the neck that gradually increases in size, which may be discovered unintentionally by themselves or during physical examination, or during ultrasound or other examinations. On physical examination, the cancer is mostly hard, with smooth surface and clear border. If the cancer is confined to the thyroid gland, it can move up and down with swallowing; if it has invaded the trachea or adjacent tissues, it is more fixed.
Ultrasound can be very helpful in the diagnosis of differentiated thyroid cancer. Most differentiated thyroid cancers are substantial masses on ultrasound, but some can be mixed masses with predominantly parenchymal components. Papillary thyroid carcinoma is mostly hypo- or very hypoechoic on ultrasound, with microcalcifications in the parenchyma. Follicular carcinoma of the thyroid gland is mostly a very homogeneous hyperechoic mass with abundant blood supply. The size of the mass, whether the boundary is clear and whether the shape is regular are not important indicators to determine whether the mass is malignant. Nowadays, fine-needle aspiration cytology (FNA) can be performed under ultrasound to further clarify the diagnosis of thyroid cancer.
Generally, differentiated thyroid carcinoma shows more cold nodules on isotope scan. If differentiated thyroid cancer is suspected to have lymph node metastasis or invasion of surrounding organs such as trachea and esophagus, CT examination can be performed to understand the extent of lymph node metastasis and invasion of organs such as trachea and esophagus to facilitate the surgical plan.
Papillary thyroid cancer is mostly metastasis to lymph nodes. The lymph nodes in the neck can be divided into zones I-VI. Generally, lymph nodes in zones II-VI are related to thyroid cancer metastasis. Usually, lymph nodes in area VI are also called central group lymph nodes, including tracheoesophageal groove, pre-tracheal and anterior laryngeal lymph nodes; lymph nodes in area II-V are also called lateral cervical area lymph nodes, including lymph nodes around large blood vessels in the neck and lymph nodes around paraneoplastic nerves. The central group of lymph nodes is usually difficult to detect by neck ultrasound because they are mostly located behind the thyroid gland and have a small diameter, while the lymph nodes in the lateral cervical region can be detected by ultrasound for metastasis. In most cases, papillary thyroid cancer on one side mostly metastasizes to the lymph nodes on the same side, but occasionally it may also metastasize to the lymph nodes on the opposite side. The route of lymph node metastasis is usually to the central group of lymph nodes first and then to the lymph nodes in the lateral cervical region; however, some cancers such as those located in the upper pole of the thyroid gland may first metastasize to the lymph nodes in the lateral cervical region. The literature reports that the metastasis rate of central group lymph nodes is usually about 50%, regardless of the size of the tumor. In view of this, the latest guidelines for differentiated thyroid cancer in China emphasize the clearance of central group lymph nodes. However, the extent of thyroid resection can be individualized according to the stage of the tumor, local medical conditions and the patient’s awareness of the disease, but at least the lateral lobe + isthmus of the affected gland should be removed.
Follicular carcinoma of thyroid mostly metastasizes to lung, bone, brain, liver and other organs through hematologic distant metastasis. A more reasonable surgical plan is to perform total/near total thyroid excision and lymph node dissection of the affected central group bilaterally, followed by iodine 131 treatment. However, since follicular carcinoma is often difficult to identify in intraoperative frozen pathology, additional surgery is often required.
According to foreign experience, since differentiated thyroid cancer has a better prognosis, if surgical resection is complete, postoperative treatment is supplemented with iodine 131 for consolidation. After iodine therapy, lifelong suppressive therapy with thyroxine preparations can often achieve a curative effect. However, for differentiated thyroid cancer with more residual thyroid gland after surgery, since iodine therapy cannot achieve the effect of consolidation therapy, and the discontinuation of thyroxine preparation during repeated iodine therapy may cause tumor recurrence or dedifferentiation, thyroxine preparation for suppressive therapy is mostly recommended for patients with more residual thyroid gland. As for the dosage of thyroxine suppressive therapy, it depends on the stage of the tumor.
Medullary thyroid carcinoma is a moderate malignant tumor that occurs in the C-cells of the thyroid gland. It can be classified as disseminated, familial and MEN2 type. The main presentation of patients is a painless hard solid nodule in the thyroid gland with localized lymph node enlargement. Sometimes the swollen lymph nodes become the first symptom. Some patients with medullary thyroid cancer may present with diarrhea, abdominal pain and flushing. On physical examination, the goiter is hard, with unclear borders and an unsmooth surface. Most sporadic goiters are on one side, while familial and MEN2 types can be bilateral.
Medullary thyroid carcinoma has elevated serum calcitonin levels and some patients have elevated carcinoembryonic antigen (CEA) levels. ultrasound indicates that most of the masses are located in the upper part of the thyroid gland and may be solitary or multiple, hypoechoic, with calcification in the center of the mass, and the nodule has no acoustic halo and is rich in blood supply.
Medullary thyroid carcinoma can develop lymphatic metastasis at an early stage and distant metastasis can occur through bloodstream, so the prognosis is worse than differentiated thyroid carcinoma. Since medullary carcinoma has no effect on thyroxine preparation and iodine 131 treatment, surgery is the most effective treatment for medullary carcinoma. The scope of surgical resection should include total excision of both thyroid glands and lymph node dissection of the central group on the side of the affected cancer; lymph node dissection of the lateral cervical region is necessary if metastasis of the lymph nodes is found before surgery. However, for familial medullary carcinoma, even if no cervical lymph node metastasis is found, prophylactic cervical lymph node dissection can be performed. Since thyroid function is absent after surgery for medullary carcinoma, thyroxine preparations must be given as replacement therapy.
Undifferentiated thyroid carcinoma is a highly malignant tumor, most often seen in older patients, usually over 65 years of age. The majority of patients present with a sudden onset of a neck lump that is hard, uneven, poorly defined, poorly mobile and rapidly increasing in size. It may be associated with hoarseness, dyspnea and dysphagia, and localized lymph node enlargement, and may appear as a heterogeneous mass with unclear borders on ultrasound, often involving the entire lobe or gland. In most cases, necrotic areas may be present.
Because of the high malignancy of undifferentiated thyroid cancer, the disease develops very rapidly and easily invades the surrounding organs and tissues such as trachea, esophagus, nerves and blood vessels in the neck, therefore, it is often diagnosed at an advanced stage and cannot be removed surgically. In recent years, some people advocate that for early stage undifferentiated thyroid cancer, if the primary foci are small, lobectomy or total thyroidectomy can be performed, followed by external radiation and chemotherapy, which can also achieve very good results.