Chapter 25 Treatment of Thyroid Disorders

Graves disease

An autoimmune disorder that causes hyperthyroidism.

Hashimoto disease

An autoimmune disorder that causes hypothyroidism.

Hyperthyroidism

A condition in which there is an excessive production of thyroid hormones.

Hypothyroidism

A condition in which there is insufficient production of thyroid hormones.

Thyroid-releasing factor

A hormone released by the hypothalamus that stimulates the pituitary gland to release thyroid-stimulating hormone.

Thyroid-stimulating hormone

A hormone released by the pituitary gland that stimulates the thyroid gland to produce and release thyroid hormones.

Tetraiodothyronine

The most abundant thyroid hormone. It contains four atoms of iodine and is also known as thyroxine.

Triiodothyronine

A hormone secreted by the thyroid gland containing three atoms of iodine.

Drug class of methimazole and propylthiouracil

Thioamides

Thyroid hormone interaction: Ferrous products (iron supplements)

Decrease the absorption of thyroid hormones.

Thyroid hormone interaction: Calcium supplements and dairy products

Decrease the absorption of thyroid hormones.

Thyroid hormone interaction: Proton pump inhibitors (e.g., omeprazole)

Decrease the absorption of thyroid hormones.

Thyroid hormone interaction: Raloxifene

Decreases the absorption of thyroid hormones.

Thyroid hormone interaction: Cholestyramine

Decreases the absorption of thyroid hormones.

Thyroid hormone interaction: Colestipol

Decreases the absorption of thyroid hormones.

Thyroid hormone interaction: Oral contraceptives

Increase thyroid-binding globulin, which may require an increased thyroid hormone dose.

Thyroid hormone interaction: Phenytoin

Increases thyroid hormone metabolism, which may require an increased thyroid hormone dose.

Thyroid hormone interaction: Carbamazepine

Increases thyroid hormone metabolism, which may require an increased thyroid hormone dose.

Warning label for methimazole

AVOID PREGNANCY.

Prevalence of thyroid disorders by gender

More prevalent in women than in men.

Hypothyroidism incidence and age

The incidence of hypothyroidism increases with age.

Autoimmune disease and thyroid risk

Patients with autoimmune diseases (e.g., type 1 diabetes) have an increased risk.

Cigarette smoking and thyroid disease

Increases the risk for developing thyroid-related eye disease.

Primary functions of thyroid hormones

They regulate growth and metabolism in almost all body cells.

Unique storage property of the thyroid gland

It is one of the few glands that produces and stores its hormones.

Mechanism of radioactive iodine (¹³¹I)

Selectively taken up by the thyroid, causing glandular destruction without damaging other tissues.

Long-term effect of ¹³¹I therapy

Most patients develop hypothyroidism, requiring lifelong thyroid replacement therapy.

Contraindication for radioactive iodine therapy

Contraindicated in pregnant women because it can cause fetal thyroid damage.

Regulation of radioactive iodine ¹³¹I

Made in nuclear pharmacies and regulated by the Nuclear Regulatory Commission.

Mechanism of action: Propylthiouracil vs. Methimazole

Both block T₄/T₃ synthesis; propylthiouracil also blocks T₄ to T₃ conversion.

Most commonly prescribed drug for hypothyroidism

Levothyroxine (synthetic T₄), which is the principal treatment.

Metabolism of levothyroxine in the body

Converted to liothyronine, just as naturally occurring T₄ is metabolized to T₃.

Levothyroxine strengths safety feature

The various strengths are color-coded to help avoid dispensing errors.