Hypothyroidism
Big picture
Hypothyroidism is a state of insufficient thyroid hormone effect. Clinically, the body “slows down”:
fatigue + cold intolerance + weight gain + constipation + dry skin + bradycardia = hypothyroidism until proven otherwise.
The most common cause in iodine-sufficient countries is Hashimoto autoimmune thyroiditis. The most important exam distinction is:
| Type | Problem | TSH | Free T4 |
|---|---|---|---|
| Primary hypothyroidism | Thyroid gland failure | High | Low |
| Subclinical primary hypothyroidism | Early thyroid failure | High | Normal |
| Central hypothyroidism | Pituitary/hypothalamic failure | Low/normal/inappropriately normal | Low |
The standard treatment is levothyroxine, and the American Thyroid Association recommends levothyroxine as the treatment of choice because of efficacy, safety, long half-life, good absorption, and low cost. ([PMC][1])
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