The thyroid gland in your neck regulates metabolism. Thyroid disorders are often undiagnosed because symptoms resemble other conditions.
Hypothyroidism (underactive): chronic fatigue, weight gain without overeating, dry skin, hair loss, constipation, persistent cold, mild depression, heavy periods. Common in women ≥40.
Hyperthyroidism (overactive): weight loss despite good appetite, palpitations, tremor, anxiety/insomnia, excessive sweating, bulging eyes, light/irregular periods.
Diagnostic tests: TSH (most sensitive), FT4, FT3, anti-TPO (for autoimmune), thyroid ultrasound if nodules.
Screening recommended: women >35, family history of thyroid disease, pregnancy, persistent symptoms >3 weeks.