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Q1: A 45-year-old woman presents with fatigue, cold intolerance and a firm diffuse goitre. TSH 22 mIU/L, free T4 low. (2 min)
- Diagnosis and antibody: overt primary hypothyroidism due to chronic autoimmune (Hashimoto) thyroiditis; anti-TPO positive in about 90%.
- Bedside signs to elicit: slow-relaxing (hung-up) ankle reflexes, bradycardia, periorbital puffiness, cool dry skin, carotenaemia.
- Why the goitre is firm: lymphocytic infiltration with germinal centres and Hurthle cell metaplasia — distinguishes from soft iodine-deficiency goitre.
Q2: Definitive management — drug, dose, monitoring. (3 min)
- Oral levothyroxine at about 1.6 mcg/kg/day (100 to 150 mcg) in a young healthy adult.
- Fasting, 30 to 60 minutes before breakfast; separate from calcium, iron, PPI, oestrogen by 4 hours.
- Recheck TSH at 6 to 8 weeks after any change; 6 to 12 monthly once stable; lifelong.
- Subclinical thresholds: TSH over 10 treat; 4.5 to 10 individualise (treat if symptomatic, anti-TPO positive, goitre, pregnant, dyslipidaemic).
- Low-and-slow (25 mcg start) in the elderly and ischaemic heart disease to avoid precipitating angina/atrial fibrillation.
- T4/T3 combination therapy: not routine; a monitored trial may be considered in well-replaced but symptomatic patients.
Q3: How does central hypothyroidism differ — and what is the critical management principle? (2 min)
- Biochemistry: low/inappropriately normal TSH + low free T4 — a normal TSH with low free T4 is never normal.
- Cause: pituitary adenoma, Sheehan, infiltrative disease, surgery/radiation.
- Always check cortisol first — coexisting ACTH deficiency is common; give hydrocortisone before levothyroxine to avoid precipitating adrenal crisis.
- Monitor to free T4 (not TSH) — pituitary MRI and full anterior-pituitary panel.
Q4: A 70-year-old with untreated hypothyroidism is brought in drowsy, core temperature 32 degrees C, sodium 122. (3 min)
- Diagnosis: myxoedema coma (altered mental status + decompensated hypothyroidism + precipitant, with hypothermia, hypoventilation, hyponatraemia).
- Resuscitation bundle: secure airway and ventilatory support for hypercapnia; IV hydrocortisone 100 mg stat then 50 mg every 6 hours (after sending cortisol/ACTH); IV levothyroxine 200 to 500 mcg loading then 50 to 100 mcg daily; passive (not active) rewarming; treat the precipitant (empirical antibiotics for infection); cautious correction of hyponatraemia and hypoglycaemia; avoid sedatives/opioids; ICU.
- Why hydrocortisone first: coexisting autoimmune adrenal insufficiency (Schmidt) or ACTH deficiency is common; giving levothyroxine alone precipitates adrenal crisis.
- Mortality 20 to 60% despite appropriate treatment.
Q5: Pregnancy and hypothyroidism — what changes? (2 min)
- Levothyroxine requirement rises 25 to 30% from weeks 4 to 6 (raised TBG, placental D3, fetal demand).
- Increase the dose at confirmation of pregnancy (two extra tablets per week is a practical rule).
- Trimester-specific TSH targets: first trimester under 2.5 mIU/L; second and third under 3.0 mIU/L.
- Check TSH each trimester and 4 to 6 weeks postpartum, then reduce to the pre-pregnancy dose.
- Untreated overt hypothyroidism: miscarriage, pre-eclampsia, preterm birth, impaired fetal neurodevelopment (maternal T4 essential before the fetal thyroid functions).
- Monitor free T4 (not total) — total T4 is falsely abnormal because of raised TBG.