Overview
Definition
A condition in which the thyroid gland does not produce enough thyroid hormones to meet the body's needs. Hashimoto's is the most common cause in iodine-sufficient areas.
Epidemiology
Affects women 5-10 times more often than men. Prevalence increases with age.
Etiology & Risk Factors
- Autoimmune destruction of the thyroid gland (Hashimoto's)
- Iodine deficiency (most common cause worldwide)
- Iatrogenic (post-thyroidectomy or post-radioiodine therapy)
- Medications (Amiodarone, Lithium)
Clinical Symptoms
- Fatigue and lethargy
- Weight gain despite decreased appetite
- Cold intolerance
- Constipation
- Dry skin, brittle hair, and hair loss (outer third of eyebrows - Queen Anne's sign)
- Bradycardia
Clinical Approach
Diagnosis
- TSH (Thyroid Stimulating Hormone): Elevated (primary screening test)
- Free T4: Decreased
- Antibodies: Anti-Thyroid Peroxidase (Anti-TPO) and Anti-Thyroglobulin antibodies are highly positive in Hashimoto's
Management
- Levothyroxine (T4 replacement) - titrate dose to normalize TSH
- Check TSH every 6 weeks after dose adjustments
Complications
- Myxedema Coma (life-threatening severe hypothyroidism causing hypothermia, bradycardia, and altered mental status)
- Dyslipidemia (increased LDL) leading to accelerated atherosclerosis
- Increased risk of B-cell lymphoma of the thyroid (in Hashimoto's)