1. Failure of the thyroid gland to manufacture and release sufficient thyroid hormone.


[The diagnosis is established by an elevated TSH.]

2. Autoimmune hypothyroidism: Leading cause of thyroid disease n developed countries, where iodine deficiency is rare because of the use of iodized salt. A autoimmune disorders are a

Hashimoto Thyroiditis.

Graves Disease

3. Iatrogenic: 131I treatment, subtotal or total thyroidectomy, external irradiation of neck for lymphoma or cancer


Drugs: iodine excess (including iodine-containing contrast media and amiodarone), lithium, antithyroid drugs, p-aminosalicylic acid, interferon α and other cytokines, aminoglutethimide, tyrosine kinase inhibitors (e.g., sunitinib)


Congenital hypothyroidism: absent or ectopic thyroid gland, dyshormonogenesis,

TSH-R mutation In addition, inherited human disorders resulting in mutations in the thyroid hormone receptor, which may abolish hormone binding, have been reported. These individuals exhibit symptoms of hypothyroidism as well as a high incidence of attention-deficit disorder. This trait is genetically dominant, indicating that the mutant receptors act in a dominant negative manner.


Iodine deficiency; Dietary iodine deficiency is endemic in several areas of the world, particularly high mountain plateaus. Supplementation of salt with iodine eliminates this dietary deficiency. The recommended dietary allowance of iodine is 40-50 mcg daily in infants, 70-120 mcg daily for children, and 150 mcg daily for adolescents and adults.

Infiltrative disorders: amyloidosis, sarcoidosis, hemochromatosis, scleroderma, cystinosis, Riedel’s thyroiditis

Overexpression of type 3 deiodinase in infantile hemangioma and other tumors

Silent thyroiditis, including postpartum thyroiditis
Subacute thyroiditis
Withdrawal of supraphysiologic thyroxine treatment in individuals with an intact thyroid
After 131I treatment or subtotal thyroidectomy for Graves’ disease
Hypopituitarism: tumors, pituitary surgery or irradiation, infiltrative disorders, Sheehan’s syndrome, trauma, genetic forms of combined pituitary hormone deficiencies
Isolated TSH deficiency or inactivity
Bexarotene treatment
Hypothalamic disease: tumors, trauma, infiltrative disorders, idiopathic

Abbreviations: TSH, thyroid-stimulating hormone; TSH-R, TSH receptor.


May present with an indolent course, or it may induce dramatic mental changes such as coma or pericardial effusion with tamponade.

Hypothyroidism is quite common in older adults

The treatment is by thyroxine replacement. (how much)



A 25-year-old woman sought treatment for her constant fatigue, lethargy, and depression.

She was small in stature and had previously been diagnosed with attention-deficit/hyperactivity disorder. On physical examination she was found to have an enlarged thyroid gland (goiter). Blood tests revealed elevated levels of T3, T4, and TSH, yet she did not exhibit typical symptoms of hyperthyroidism. Which one of the following possibilities offers the most likely explanation of her symptoms?

Thyroid hormone overproduction because of a thyroid gland tumor

Hypersecretion of TSH because of a pituitary tumor

Genetic alteration in the thyroid receptor reducing its ability to bind thyroid hormone

Mutation in the TSH receptor in the thyroid gland reducing its ability to bind TSH

Iodide deficiency in the diet

The correct answer is C.

C The patient exhibits symptoms of hypothyroidism including goiter, yet thyroid hormone levels are elevated. This pattern can only be explained by resistance of target cells to thyroid hormone, for example, a mutation of the receptor decreasing its binding affinity for hormone. Iodide deficiency would lead to goiter but not increased hormone levels.



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