Endocrine system: pituitary hormones, thyroid hormones
Physiology · MBBS
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A woman gains weight, feels cold and tired; TSH is high, T4 low. High TSH with low T4 means primary hypothyroidism — the thyroid itself is failing (often Hashimoto's autoimmune attack), and the pituitary shouts louder (raised TSH) trying to drive it. Symptoms are metabolism slowed: fatigue, weight gain, cold intolerance, constipation, slow heart. Daily thyroxine replacement restores levels — the feedback loop is the diagnostic key: the pattern of TSH vs T4 locates the fault.
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