Clinical meaning
Thyroid disorders involve HPT axis dysregulation. Hashimoto (anti-TPO antibodies) causes hypothyroidism through lymphocytic infiltration and follicular destruction. Graves (TSI/TRAb) causes hyperthyroidism via TSH receptor stimulation. TSH is the best screening test. Levothyroxine 1.6 mcg/kg/day for hypothyroidism; check TSH at 6-8 weeks after dose changes. Toxic multinodular goiter develops from autonomous nodules producing excess thyroid hormone independently of TSH.
Diagnosis & workup
Diagnostics & workup: - IGF-1 for growth hormone excess or deficiency screening - Fasting glucose and 2-hour OGTT for diabetes diagnosis - Morning cortisol (8 AM) and ACTH for adrenal function - Thyroid ultrasound for nodule characterization (TI-RADS scoring) - 24-hour urine free cortisol for Cushing confirmation - Plasma metanephrines for pheochromocytoma screening - PTH with calcium and phosphorus for parathyroid evaluation
Risk factors: - Pregnancy altering hormonal milieu (gestational DM, thyroiditis) - Age-related hormonal decline (menopause, andropause) - Chronic corticosteroid use with HPA axis suppression - Chronic kidney disease affecting calcium-phosphorus-PTH axis - MEN syndrome family history - Eating disorders with hypothalamic amenorrhea - Medication-induced endocrinopathy (lithium-thyroid, statin-DM)