Introduction
Nodular goiter (NG) is a nodular enlargement of the thyroid gland characterized by excessive hyperplasia of the thyroid tissue and structural and functional changes in one or more areas of normal thyroid tissue. In cases where thyroid insufficiency, autoimmune thyroid disease, thyroiditis and thyroid tumors are excluded, it may be referred to as simple nodular goiter (SNG). The pathological changes depend on the severity and duration of the disease. In the early stages of the disease, hyperplastic, dilated follicles are more evenly distributed in the gland, forming a diffuse goiter; as the lesion persists or repeatedly worsens, the dilated follicles accumulate into multiple nodules of varying sizes, forming a nodular goiter. When some nodules degenerate due to poor blood supply, they may also cause cysts, internal bleeding, fibrosis and calcification. Heterogeneity of thyroid structure and function and a certain degree of functional autonomy are characteristic of the later stages of the disease.
[Etiology].
Environmental iodine deficiency is the main environmental factor causing goiter simplex. Insufficient iodine intake prevents the synthesis of sufficient thyroid hormones, which in turn feedback causes increased TSH secretion from the pituitary gland and stimulates thyroid hyperplasia and compensatory enlargement. Other environmental factors include: high iodine, smoking, naturally occurring goitrogens, emotional stress, medications and infections.
Some adolescents, pregnant or menopausal women can develop a mild diffuse goiter, called physiologic goiter, due to an increased need for thyroxine.
Women are more susceptible to the disease, and the ratio of women to men in non-endemic goiter areas can be 5 to 10:1.
Treatment
The main treatment methods include: iodine supplementation therapy, conservative therapy, surgery, radioactive I131 therapy, etc.
1. Iodine supplementation therapy.
For physiological goiter, iodine supplementation or iodine-rich foods such as kelp and nori can be used; for non-physiological nodular goiter, iodine supplementation is not recommended because it may induce hyperthyroidism and increase the incidence of lymphocytic thyroiditis and papillary thyroid cancer.
2. L-T4 suppression therapy.
For patients with diffuse goiter under 20 years old, small doses of thyroxine can be given to alleviate hyperplasia or hypertrophy of the thyroid gland through feedback inhibition of TSH secretion in the anterior pituitary gland. The commonly used dose is levothyroxine: 50-100ug/d or thyroid tablets: 40-120mg/d for 3-6 months as a course of treatment. L-T4 suppression therapy is also feasible for patients with nodular goiter who have mild lesions and are unwilling or unable to tolerate surgery. The effectiveness of L-T4 suppression therapy depends on the extent to which TSH is suppressed, and the ideal dose of oral L-T4 is currently more widely accepted: TSH is controlled at 0.1 to 0.3 mU/L, and T3 and T4 are controlled within the high limit of normal values. However, it should be noted that in three clinical trials, the results showed that only a small number of patients with nodular goiter were effective for L-T4 suppression therapy; in addition, there is a risk of subclinical hyperthyroidism, osteoporosis, induced atrial fibrillation, and menstrual disorders during the long-term use of L-T4, so the selection of indications and the duration of L-T4 suppression therapy should be carefully, especially for postmenopausal women.
3.Surgical therapy.
Surgical treatment has the advantages of rapidly reducing the symptoms of compression, normalizing the volume of the enlarged thyroid gland, and clarifying the pathological diagnosis.
Indications for surgery
(1) Nodular goiter with compression symptoms: some of the compression symptoms caused by nodular goiter are reversible, such as: narrowing of the trachea by compression, compression of the esophagus, compression of the internal jugular vein and superior vena cava; once the compression is released, the above symptoms will be rapidly relieved or disappear; some of the symptoms are irreversible, such as the nerves of the recurrent laryngeal nerve, sympathetic nerve chain or phrenic nerve have degenerated due to prolonged compression, and even if the compression is Even if the compression is removed, the above symptoms will continue to exist
(2) Post-thoracic goiter with compression symptoms: Post-thoracic goiter is a goiter with more than 50% of its volume located below the entrance to the thorax, and surgery is the only effective method. There are generally 3 types: Type I is incomplete retrosternal goiter; Type II is complete retrosternal goiter; and Type III is intrathoracic vagal goiter whose blood supply is related to the intrathoracic vessels. Types I and II are due to the combined effect of the goiter’s own gravity, swallowing activity and negative pressure in the thoracic cavity, causing it to drop down into the thoracic cavity along the anterior tracheal space, and its blood supply still comes from the superior and inferior thyroid arteries and their branches. Because the left side of the retrosternal sternum is blocked by the aortic arch and the left common carotid artery, a right-sided retrosternal goiter is more common in clinical practice. The majority of type I and II retrosternal goiters can be removed through a cervical surgical approach; type III can be removed through a combined cervicothoracic approach.
(3) Secondary hyperthyroidism: Simple goiter (5%-8%) can show symptoms of hyperthyroidism, also known as toxic multinodular goiter, which starts slowly, mostly in the elderly or those taking large amounts of iodine, often with prominent cardiovascular symptoms, such as: arrhythmia, heart failure, etc., wasting and weakness is obvious, and may be accompanied by anorexia. The surgical treatment should be performed in strict accordance with the preoperative preparation of hyperthyroidism, and total thyroidectomy or near-total thyroidectomy is appropriate. Surgery has been gradually replaced by radioactive I131 therapy to reduce the risk of surgery and postoperative complications.
(4) Nodular goiter with suspected malignancy: There is no conclusive evidence that nodular goiter is pre-cancerous, but 4% to 17% of surgically removed nodular goiter specimens are associated with thyroid cancer. A patient with a nodular goiter should be highly suspected of having thyroid cancer if it is accompanied by.
(i) a family history of medullary thyroid cancer or multiple endocrine adenoma syndrome;
(ii) Rapid growth of the mass (especially during L-T4 treatment);
(iii) fixed masses;
④Adhesion to surrounding tissues;
⑤ Vocal cord paralysis;
(6) enlargement of adjacent lymph nodes;
(vii) distant metastasis (lung or bone). Moderate suspicion of thyroid cancer includes
①Age less than 20 years old or more than 60 years old;
②Male;
(iii) Isolated nodules;
④History of radiation to the head and neck;
⑤ hard texture;
(⑥Compression symptoms: dysphagia, dysphonia, hoarseness, dyspnea and cough.
(5) Nodular goiter affecting appearance: superficially located nodular goiter protruding from the anterior cervical region, especially in the isthmus, affecting appearance, and patients urgently requesting surgery.
Mode of surgery.
The choice of surgical approach should be determined by the number, size and distribution of nodules. For single nodular goiter, removal of the mass, partial lobectomy or total unilateral lobectomy is feasible; for multiple nodular goiters, subtotal thyroidectomy and total thyroidectomy are also feasible. The specific procedures are.
(1) Total thyroidectomy: It is the main surgical procedure recommended by general surgery and surgical oncology in Europe and the United States at present. Although this procedure can effectively avoid intraoperative mass omission and postoperative recurrence, it also has its disadvantages: a permanent hypothyroidism; b hypoparathyroidism due to intraoperative parathyroid gland miscutting; c serious complications such as increased probability of laryngeal nerve injury. Therefore, the indications should be strictly controlled.
① Bilateral nodular goiter with suspected bilateral thyroid cancer;
(ii) Bilateral nodular goiter with intraoperative finding that normal thyroid tissue cannot be preserved;
(3) Nodular goiter with secondary hyperthyroidism.
(2) Thyroid lobectomy: The indications for surgery are
(1) Nodular goiter mainly located in one lobe and normal gland cannot be preserved in the affected gland;
(2) If the nodular goiter is located in one gland and there is a suspicion of thyroid cancer on the affected side.
(3) Subtotal thyroidectomy: if the nodular goiter lesion is located in the bilateral thyroid gland and some normal thyroid tissue can be preserved.
(4) Mass excision of thyroid gland: Mass excision is feasible for solitary nodular goiter, and attention should be paid to the exploration of the gland surrounding the mass and the contralateral thyroid gland during surgery.
Once thyroid cancer is found, it should be treated according to thyroid cancer: removal of the ipsilateral gland, isthmus and clearance of lymph nodes in the central area to avoid secondary surgery.
Principles of postoperative follow-up.
To avoid recurrence, a small oral dose of L-T4 (50-100ug) is recommended after surgery, with follow-up every 3-6 months (including physical examination, thyroid and neck ultrasound, and thyroid function). To reduce unnecessary side effects, the L-T4 dose should be adjusted according to thyroid function during the follow-up. If malignancy is clinically considered as a possibility, CT examination of the neck (plain + enhanced) should be added.
4. Radioactive I131 therapy.
Indications for treatment: For patients with postoperative recurrence of nodular goiter and still needing further treatment, radioactive I131 therapy can be switched to avoid serious surgical complications. Radioactive I131 therapy is also an option for patients with large nodular goiters or nodular goiters with hyperthyroidism who do not want to undergo surgery or cannot tolerate surgery.
Patients who have relapsed after surgery and still need further treatment may be switched to radioactive I131 therapy to avoid serious surgical complications. Radiation I131 therapy may also be chosen for patients with giant nodular goiter or nodular goiter with hyperthyroidism who do not want to undergo surgery or cannot tolerate surgery.