was ist ft3 — what symptoms are typical?

FT3 (free triiodothyronine) is the active thyroid hormone that regulates metabolism. Typical symptoms of elevated FT3 (hyperthyroidism) include palpitations, weight loss despite increased appetite, heat intolerance, excessive sweating, tremor, anxiety, insomnia, and frequent bowel movements. Low FT3 (hypothyroidism) presents with fatigue, lethargy, weight gain, cold intolerance, dry skin, constipation, poor concentration, and depressed mood. Caveat: FT3 alone is insufficient for diagnosis; it must be interpreted alongside TSH, fT4, and possibly antibodies (TPO, TRAK). Non-thyroidal illness (e.g., renal failure, malnutrition) can also lower FT3. Always consult an endocrinologist for proper assessment. Evidence is strong (clinical endocrinology).