(See also Overview of Thyroid Function Overview of Thyroid Function The thyroid gland, located in the anterior neck just below the cricoid cartilage, consists of 2 lobes connected by an isthmus. Follicular cells in the gland produce the 2 main thyroid hormones... read more .)
The reported incidence of thyroid nodules varies with the method of assessment. In middle-aged and older patients, palpation reveals nodules in about 5%. Results of ultrasonography and autopsy studies suggest that nodules are present in about 50% of older adults. Many nodules are found incidentally on head and neck imaging studies done for other disorders.
Etiology
Most nodules are benign. Benign causes include
Hyperplastic colloid goiter
Thyroid cysts
Thyroiditis
Thyroid adenomas
Evaluation of a Thyroid Nodule
History
Thyroid nodules may be painful or asymptomatic. Pain suggests thyroiditis or hemorrhage into a cyst. An asymptomatic nodule may be malignant but is usually benign.
Symptoms of hyperthyroidism Hyperthyroidism Hyperthyroidism is characterized by hypermetabolism and elevated serum levels of free thyroid hormones. Symptoms include palpitations, fatigue, weight loss, heat intolerance, anxiety, and tremor... read more 
(ie, palpitations, heat intolerance, weight loss, tremors) suggest a hyperfunctioning adenoma or thyroiditis, whereas symptoms of hypothyroidism Hypothyroidism Hypothyroidism is thyroid hormone deficiency. Symptoms include cold intolerance, fatigue, and weight gain. Signs may include a typical facial appearance, hoarse slow speech, and dry skin. Diagnosis... read more 
(ie, cold intolerance, weight gain, fatigue) suggest Hashimoto thyroiditis Hashimoto Thyroiditis Hashimoto thyroiditis is chronic autoimmune inflammation of the thyroid with lymphocytic infiltration. Findings include painless thyroid enlargement and symptoms of hypothyroidism. Diagnosis... read more .
Risk factors for thyroid cancer include
History of thyroid irradiation, especially in infancy or childhood
Age < 20 years
Male sex
Family history of thyroid cancer Thyroid Cancers There are 4 general types of thyroid cancer. Most thyroid cancers manifest as asymptomatic nodules. Rarely, lymph node, lung, or bone metastases cause the presenting symptoms of small thyroid... read more or multiple endocrine neoplasia type 2 Overview of Multiple Endocrine Neoplasias (MEN) The multiple endocrine neoplasia (MEN) syndromes comprise 3 genetically distinct familial diseases involving adenomatous hyperplasia and malignant tumors in several endocrine glands. MEN 1 involves... read more
A solitary nodule
Dysphonia
Increasing size (particularly rapid growth or growth while receiving thyroid suppression treatment)
Physical examination
Signs that suggest thyroid cancer include stony, hard consistency or fixation to surrounding structures, cervical lymphadenopathy, and hoarseness (due to recurrent laryngeal nerve paralysis).
Testing
Initial evaluation of a thyroid nodule consists of testing for Laboratory Testing of Thyroid Function The thyroid gland, located in the anterior neck just below the cricoid cartilage, consists of 2 lobes connected by an isthmus. Follicular cells in the gland produce the 2 main thyroid hormones... read more
Thyroid-stimulating hormone (TSH)
Antithyroid peroxidase antibodies
If thyroid-stimulating hormone (TSH) is low (consistent with hyperthyroidism), radioiodine scanning is done. Nodules with increased radionuclide uptake (hot) are seldom malignant.
If thyroid function tests do not indicate hyperthyroidism Hyperthyroidism Hyperthyroidism is characterized by hypermetabolism and elevated serum levels of free thyroid hormones. Symptoms include palpitations, fatigue, weight loss, heat intolerance, anxiety, and tremor... read more or Hashimoto thyroiditis Hashimoto Thyroiditis Hashimoto thyroiditis is chronic autoimmune inflammation of the thyroid with lymphocytic infiltration. Findings include painless thyroid enlargement and symptoms of hypothyroidism. Diagnosis... read more , the next step is to examine the nodule with a thyroid ultrasound.
Ultrasonography is useful in determining the size of the nodule, but may not allow a distinction between a benign or malignant lesion. Thyroid cancer is suggested by nodule hypoechogenicity; marked internal vascularity; irregular borders; height of the nodule being greater than the width; irregular macrocalcifications; fine, stippled psammomatous microcalcifications (papillary thyroid carcinoma); or dense, homogenous irregular calcification (medullary thyroid carcinoma).
For nodules with suspicious features, fine-needle aspiration biopsy (FNAB) done under ultrasound guidance is the procedure of choice and the most economical means to distinguish benign from malignant nodules. FNAB is generally not recommended for nodules <1 cm or for nodules that are entirely cystic.
Cytologic examination of the cells obtained from FNAB may distinguish benign from malignant lesions. For lesions that are cytologically indeterminate, molecular analysis of the FNAB aspirate for mutations and rearrangements, or measurement of calcitonin for possible medullary carcinoma may add sufficient diagnostic clarity to allow an optimally informed treatment recommendation.
Treatment of a Thyroid Nodule
Treatment of underlying disorder
Treatment is directed at the underlying disorder (1 Treatment reference Thyroid nodules are benign or malignant growths within the thyroid gland. They are common, increasingly so with increasing age. (See also Overview of Thyroid Function.) The reported incidence... read more ). Nodules in patients with Hashimoto thyroiditis or other causes of goiter associated with hypothyroidism may stabilize or shrink with thyroxine replacement in doses that render the patient euthyroid. For small benign nodules not associated with hypothyroidism, thyroxine suppression of TSH effectively shrinks the nodule in no more than half the cases, and is seldom done. Thyroxine is not used to treat cancerous nodules Thyroid Cancers There are 4 general types of thyroid cancer. Most thyroid cancers manifest as asymptomatic nodules. Rarely, lymph node, lung, or bone metastases cause the presenting symptoms of small thyroid... read more .
Large benign nodules that compress the surrounding neck structures may become smaller following radiofrequency ablation. Partial or complete thyroidectomy are effective for treating nodules that continue to grow or cause compressive symptoms.
Toxic nodules may be treated with radioactive iodine to control hyperthyroidism and reduce nodule size.
Nodules that are not due to thyroid cancer, are not causing compressive symptoms and are not associated with either hypothyroidism or hyperthyroidism may be safely followed by periodic neck examination and, if there is suspicion of nodule growth, by repeat ultrasound evaluation.
Treatment reference
1. Haugen BR, Alexander EK, Bible KC, et al: 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid 26(1): 1–133, 2016. doi: 10.1089/thy.2015.0020
