Deficient thyroid hormone production: primary (TSH ↑, T4 ↓) most common.
Causes
- • Autoimmune (Hashimoto)
- • Post-RAI / surgery / radiotherapy
- • Drugs: amiodarone, lithium, immunotherapy
- • Iodine deficiency
- • Secondary: pituitary disease
Clinical features
- • Fatigue, cold intolerance, weight gain
- • Constipation, dry skin, hair loss
- • Bradycardia, hoarse voice
- • Menorrhagia, depression
Investigations
- • TSH, free T4
- • TPO antibodies
- • Lipid profile, FBC, U&E
Management
- • Levothyroxine 1.6 mcg/kg/day (50–100 mcg starting in young, 25 mcg in elderly / IHD)
- • Recheck TSH at 6–8 weeks
- • Target TSH 0.5–2.5 in pregnancy / planning pregnancy
Complications
- • Myxoedema coma
- • Cardiovascular: HF, pericardial effusion
Clinical pearls
- • Subclinical (↑ TSH, normal T4): treat if TSH >10, symptomatic, antibody positive, pregnant
References
- • ATA Hypothyroidism 2014
Educational — verify locally.
