Decreased thyroid hormone production causing systemic slowing; TSH elevated with low/normal free T4.
History taking
- • Fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss
- • Menorrhagia, infertility, depression, hoarseness
- • Postpartum status, neck irradiation, prior thyroid surgery
- • Drugs: amiodarone, lithium, interferon
Examination
- • Bradycardia, hypothermia, puffy face, periorbital oedema
- • Goitre — diffuse (Hashimoto) or absent
- • Delayed ankle jerk, slow speech, dry coarse skin
Red flags
- • Myxoedema coma — altered sensorium, hypothermia, hypotension
- • Pericardial effusion with tamponade
- • Severe symptomatic hyponatraemia
Differential diagnosis
- • Subclinical hypothyroidism, central (pituitary) hypothyroidism
- • Depression, chronic fatigue, anaemia, nephrotic syndrome
Recommended investigations
- • TSH (screening); free T4 if TSH abnormal
- • Anti-TPO antibodies for autoimmune cause
- • Lipid profile, CBC, electrolytes, CK
- • USG thyroid only if nodule/goitre
Diagnosis
- • Overt: TSH ↑, free T4 ↓
- • Subclinical: TSH ↑ (4.5–10), free T4 normal — treat if symptomatic, pregnant, TSH>10, or anti-TPO positive
Initial treatment / management
- • Levothyroxine on empty stomach, 30–60 min before breakfast
- • Start dose 1.6 µg/kg/day in young; 25–50 µg/d in elderly/IHD
- • Recheck TSH after 6 weeks; titrate by 12.5–25 µg
Prescription examples
- • Tab Levothyroxine 50 µg PO OD (empty stomach) — adjust monthly
- • Avoid iron/calcium/PPI within 4 hours of dose
Follow-up advice
- • TSH every 6 weeks until stable, then 6–12 monthly
- • In pregnancy: TSH every 4 weeks in first half
Patient counselling
- • Lifelong therapy in most; do not skip doses
- • Take consistently on empty stomach with water
- • Inform doctor before pregnancy — dose increase usually needed
Referral criteria
- • Pregnancy, infertility, paediatric cases
- • Suspected central hypothyroidism or pituitary disease
- • Myxoedema coma — emergency
Clinical pearls
- • Check TSH 6 weeks after any dose change; don't chase short-term values
- • Generic switching can alter TSH — recheck after switch
- • Pregnancy increases requirement by ~25–30%
References
- • ATA Guidelines for Hypothyroidism 2014
- • ETA Guidelines on Subclinical Hypothyroidism 2013
Educational outpatient guide — verify against local guidelines before clinical use.
