Hypothyroidism in adults

Red Flags

Myxoedema coma — hypothermia, hypotension, hypoventilation, altered mental status — IV levothyroxine plus IV hydrocortisone in ICU^[1]
Newly diagnosed hypothyroidism with concurrent unrecognised adrenal insufficiency — give hydrocortisone first to avoid precipitating adrenal crisis on starting levothyroxine^[1]
Pregnancy with overt hypothyroidism — adverse maternal/fetal outcomes; immediate levothyroxine, target TSH <2.5 in 1st trimester^[1]
Symptomatic angina or arrhythmia in elderly starting levothyroxine — start low and titrate slowly to avoid precipitating ischaemia^[1]

First-line treatment

Interventions

Subclinical hypothyroidism management^[1]
Treat if TSH ≥10 mIU/L, pregnancy or planning pregnancy, infertility, or symptomatic with TSH 4.5–10 plus positive anti-TPO. Otherwise observation with TSH every 6–12 months
Iodine sufficiency check^[1]
Population iodisation programme has reduced iodine deficiency; residual pockets remain — check dietary iodine source where deficiency suspected
Annual TSH monitoring once stable^[1]
Once euthyroid on stable LT4 dose, check TSH annually; sooner with weight change ≥10%, pregnancy, or new medications affecting absorption

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Levothyroxine (LT4)^[1]	Synthetic thyroid hormone (T4)	1.6 mcg/kg/day PO once daily on empty stomach (typically 100–125 mcg). Lower starting dose (12.5–50 mcg) in elderly, CAD, frail; titrate every 4–6 weeks	10–15 mcg/kg/day in neonates; weight-based per age in older children	Take 30–60 minutes before food, separated from calcium, iron, PPIs by 4 hours
Levothyroxine in pregnancy^[1]	Thyroid hormone (pregnancy adjusted)	Increase pre-pregnancy dose by 25–30% on confirmation of pregnancy; monitor TSH every 4 weeks	—	Target TSH <2.5 in 1st trimester, <3.0 thereafter

Levothyroxine (LT4)^[1]

Synthetic thyroid hormone (T4)

Adult: 1.6 mcg/kg/day PO once daily on empty stomach (typically 100–125 mcg). Lower starting dose (12.5–50 mcg) in elderly, CAD, frail; titrate every 4–6 weeks
Paediatric: 10–15 mcg/kg/day in neonates; weight-based per age in older children

Take 30–60 minutes before food, separated from calcium, iron, PPIs by 4 hours

Levothyroxine in pregnancy^[1]

Thyroid hormone (pregnancy adjusted)

Adult: Increase pre-pregnancy dose by 25–30% on confirmation of pregnancy; monitor TSH every 4 weeks
Paediatric: —

Target TSH <2.5 in 1st trimester, <3.0 thereafter

Safety-net

Take levothyroxine on an empty stomach 30–60 minutes before food, with water only^[1]
Do not stop levothyroxine — hypothyroidism rebounds within weeks^[1]
If you become pregnant, contact your clinician same week — most women need a 25–30% dose increase^[1]

Referral criteria

Suspected myxoedema comaEmergency department / ICU^[1]
Pregnancy with hypothyroidismEndocrinology and obstetric medicine — joint care^[1]
Persistent symptoms despite normal TSH on adequate LT4 doseEndocrinology to consider combination LT4/LT3 trial or alternative diagnoses^[1]

Clinical summary

Indian Thyroid Society perspective on diagnosis and treatment of hypothyroidism — TSH-driven levothyroxine titration with attention to iodine status and pregnancy.

References

1.Indian Thyroid Society Guidelines for Hypothyroidism; ATA 2014 Hypothyroidism Treatment Guidelines (2021)