Hyperthyroidism

Basics

Hyperthyroidism is the result of inappropriate secretion of thyroid hormones by the thyroid gland
Occurs in ∼1.2% of the population in the U.S.
Excessive thyroid hormone production results in a continuum of disease:
- Subclinical or mild hyperthyroidism
- Thyrotoxicosis
- Thyroid storm or thyrotoxic crisis with life-threatening manifestations:
  - 1–2% of patients with hyperthyroidism
Regulation of thyroid hormone:
- Thyrotropin-releasing hormone (TRH) from hypothalamus acts on the anterior pituitary
- Thyroid-stimulating hormone (TSH) released by anterior pituitary gland and results in increased T₃ and T₄ from the thyroid gland:
  - Most of circulating hormone is T₄, which is peripherally converted to T₃
  - T₃ is much more biologically active than T₄ although it has a shorter half-life
The causes of hyperthyroidism can be broken down into 4 categories:
- Excessive thyroid stimulation
- Inappropriate thyroid hormone synthesis
- Stores of hormones are released
- Excessive sources of hormone (endogenous or exogenous)

Primary hyperthyroidism (resulting in inappropriate hormone synthesis):
- Toxic diffuse goiter (Graves’ disease)
- Toxic multinodular (Plummer disease) or uninodular goiter
- Excessive iodine intake
Thyroiditis (thyroid inflammation):
- Postpartum thyroiditis
- Radiation-induced thyroiditis
- Subacute thyroiditis (de Quervain)
- Amiodarone-associated thyroiditis
- Chronic thyroiditis (Hashimoto/lymphocytic)
Metastatic thyroid cancer
Ectopic thyroid tissue (struma ovarii)
Pituitary adenoma
Drug induced:
- Amiodarone
- Lithium
- α-interferon
- Interleukin-2
- Iodine (radiographic contrast agents)
- Excessive thyroid hormone (factitious thyrotoxicosis)
- Aspirin overdose

There's more to see -- the rest of this topic is available only to subscribers.