Hypothyroidism
Hypothyroidism occurs when the thyroid gland produces insufficient thyroid hormone, slowing metabolism and affecting nearly every organ system. It is one of the most common endocrine conditions, affecting up to 5% of the US population, and is more prevalent in women and older adults. Most cases are treated effectively with oral thyroid hormone replacement.
Symptoms
Fatigue and sluggishness, cold intolerance, unexplained weight gain, constipation, dry skin and hair, hair loss, slowed heart rate, brain fog or poor concentration, muscle aches, depression, and irregular or heavy menstrual periods.
Causes and risk
Hashimoto's thyroiditis (autoimmune destruction of the thyroid) accounts for most cases. Other causes include prior thyroid surgery or radioactive iodine ablation, certain medications (lithium, amiodarone), iodine deficiency, and -- rarely -- pituitary disorders causing secondary hypothyroidism.
How it is evaluated
TSH is the primary screening test. Elevated TSH triggers free T4 measurement. We add anti-TPO and anti-thyroglobulin antibodies to confirm Hashimoto's. Lipid panel and complete blood count may show changes consistent with untreated hypothyroidism.
Treatment
Levothyroxine (synthetic T4) taken on an empty stomach is the standard treatment. TSH is rechecked four to eight weeks after starting or adjusting the dose. Most patients feel significantly better within six to eight weeks. Combination T4/T3 therapy (adding liothyronine) is an option for patients with persistent symptoms on levothyroxine alone.