Thyroid Hormone

Thyroid hormone is released by the thyroid gland. Thyroid stimulating hormone, which is released by the pituitary gland, stimulates the thyroid to secrete thyroid hormone.  Levothyroxine is a common medication used to supplement or replace naturally released thyroid hormone in patients with hypothyroidism.  Toxicity from thyroid hormone simulates hyperthyroidism symptoms with tachycardia, nervousness, and weight loss.

Class Drugs

• Liothyronine (T3)

• Levothyroxine (T4)

Class Mechanism of Action

T4 is converted to T3 intracellularly, which is the active hormone

• T3 stimulates various receptors that promote RNA formation, which leads to protein production

• The proteins then carry out the effects of T4/T3

Class Applications

Hypothyroidism

Class Adverse Effects

Toxicity

• Nervousness

• Heat intolerance

• Weight loss

• Tachycardia

Metabolized by CYP450, so certain drugs will reduce effectiveness

Drug Table

Drug Name	Application	Comments	Image
Liothyronine		Rarely Used	"Lion" "Thyme" "Nine"
Levothyroxine			"Lever" "Thyme" "Rocks"