Simple nontoxic goiter, which may be diffuse or nodular, is noncancerous hypertrophy of the thyroid gland without hyperthyroidism, hypothyroidism, or inflammation. Except in severe iodine deficiency, thyroid function is normal and patients are asymptomatic except for an obviously enlarged, nontender thyroid. Diagnosis is clinical and with determination of normal thyroid function. Treatment is directed at the cause, but partial surgical removal may be required for very large goiters.
(See also Overview of Thyroid Function.)
Simple nontoxic goiter, the most common type of thyroid enlargement, is frequently noted at puberty, during pregnancy, and at menopause. The cause at these times is usually unclear. Known causes include
Intrinsic thyroid hormone production defects
Ingestion of foods that contain substances that inhibit thyroid hormone synthesis (goitrogens, eg, cassava, broccoli, cauliflower, cabbage), as may occur in countries in which iodine deficiency is common
Iodine deficiency is rare in North America but remains the most common cause of goiter worldwide (termed endemic goiter). Compensatory small elevations in thyroid-stimulating hormone (TSH) occur, preventing hypothyroidism, but the TSH stimulation results in goiter formation. Recurrent cycles of stimulation and involution may result in nontoxic nodular goiters. However, the true etiology of most nontoxic goiters in iodine-sufficient areas is unknown.
Symptoms and Signs of Simple Nontoxic Goiter
Patients with goiter are usually asymptomatic. Those with larger goiters may present with a dysphagia, hoarseness, or a sensation of fullness in the throat (globus pharyngis) (1). The patient may have a history of low iodine intake or overingestion of food goitrogens, but these phenomena are rare in North America.
In the early stages, the goiter is typically soft, symmetric, and smooth. Later, multiple nodules and cysts may develop.
Symptoms and signs reference
1. Sajisevi M, Caulley L, Eskander A, et al. Evaluating the Rising Incidence of Thyroid Cancer and Thyroid Nodule Detection Modes: A Multinational, Multi-institutional Analysis. JAMA Otolaryngol Head Neck Surg 2022;148(9):811-818. doi:10.1001/jamaoto.2022.1743
Diagnosis of Simple Nontoxic Goiter
Thyroidal radioactive iodine uptake
Thyroid scan
Thyroid ultrasonography
Thyroxine (T4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) levels
In the early stages, thyroidal radioactive iodine uptake may be normal or high with normal thyroid scans. Thyroid function test results are usually normal. Thyroid antibodies are measured to rule out Hashimoto thyroiditis.
In endemic goiter, serum TSH may be slightly elevated, and serum T4 may be low-normal or slightly low, but serum T3 is usually normal or slightly elevated.
Thyroid ultrasonography is done to determine whether there are nodules that are suggestive of cancer.
Treatment of Simple Nontoxic Goiter
Depends on cause
In iodine-deficient areas, eliminate iodine deficiency by these means:
Iodine supplementation of salt
Oral administration of iodized oil
Intramuscular administration of iodized oil yearly
Iodination of water, crops, or animal fodder
Any goitrogens (eg, cassava, broccoli, cauliflower, cabbage) being ingested should be stopped.
In other instances, suppression of the hypothalamic-pituitary axis with thyroid hormone blocks thyroid-stimulating hormone (TSH) production (and hence stimulation of the thyroid).
Levothyroxine is contraindicated in older patients with nontoxic nodular goiter because these goiters rarely shrink and may harbor areas of autonomy, so that levothyroxine therapy can result in hyperthyroidism.
Large goiters occasionally require surgery to shrink the gland enough to prevent interference with respiration or swallowing or to correct cosmetic problems.
Treatment with iodine-131 for large goiters is generally ineffective unless there is clear evidence of autonomous function manifested by a suppressed TSH.
Key Points
Thyroid function is usually normal.
When the cause is iodine deficiency, iodine supplementation is effective treatment.
Surgery may be needed for large goiters.
