🧬 EndocrinologyEndocrineStudentInternResident

Hypothyroidism

Also known as: underactive thyroid · low thyroid · myxoedema

Deficient thyroid hormone — fatigue, weight gain, cold intolerance, constipation, dry skin and bradycardia. Levothyroxine replacement titrated to TSH.

Source · Reviewed 2026-08-15 · v1.0— AI-assisted draft — verify against the cited guideline before clinical use.

⚕️ Education only — not medical advice. Verify against the latest official guideline and your local protocol; confirm every drug dose against the cited source before clinical use.

Who gets it

More common in women and with age; autoimmune (Hashimoto's) is the commonest cause. Also post-thyroidectomy/radioiodine, iodine deficiency and certain drugs.

Red flags — escalate / refer

Myxoedema coma — hypothermia, altered mental state, bradycardia, hypoventilation → emergency.
Known cardiac disease: start levothyroxine low and titrate slowly.

Work-up / diagnosis

1TSH is the primary test: high TSH with low free T4 = primary hypothyroidism; high TSH with normal T4 = subclinical.
2Check anti-TPO antibodies for autoimmune cause; screen lipids.
3Exclude pregnancy considerations (targets and dosing differ).

Management — overview

Levothyroxine once daily on an empty stomach; recheck TSH every 6–8 weeks and adjust until normal, then review annually.
Start low and go slow in the elderly and in cardiac disease.
Pregnancy: requirements rise — increase the dose promptly and monitor with trimester-specific TSH targets.
Subclinical hypothyroidism: decide to treat based on TSH level, symptoms, antibodies and pregnancy/planning.

In-depthFull dosing & advanced protocol

Drug dosing

Levothyroxine (LT4)

Replacement therapy

Adult dose: Full replacement ~1.6 µg/kg/day; start 25–50 µg/day in the elderly/cardiac disease and titrate by TSH
Route: Oral (empty stomach, 30–60 min before food)

Caution: Over-replacement risks atrial fibrillation and osteoporosis; separate from calcium, iron and PPIs (they impair absorption).

WHOWHO Model List of Essential Medicines (electronic EML) (2025 (24th)) ↗

Subclinical, pregnancy & myxoedema coma

Treat subclinical hypothyroidism when TSH is markedly raised, symptomatic, antibody-positive, or in pregnancy/planning.
In pregnancy, aim for trimester-specific TSH targets and increase the dose early.
Myxoedema coma: IV levothyroxine, IV hydrocortisone (until adrenal insufficiency excluded), plus supportive warming and ventilation — critical care.

ICMRStandard Treatment Workflows (STWs), India — Dept. of Health Research & ICMR (2022+) ↗

References

Guidelines change. If something here is out of date, tell us — we keep these current.

🚩 Report outdated / suggest update

More protocols

Type 2 Diabetes MellitusChronic hyperglycaemia from insulin resistance plus relative insulin deficiency — a major driver of cardiovascular, renal, eye and nerve disease.Diabetic Ketoacidosis (DKA)An acute hyperglycaemic emergency of insulin deficiency — hyperglycaemia, ketosis and metabolic acidosis. Fluids, fixed-rate insulin and potassium are the pillars of treatment.Hyperthyroidism & Thyroid StormExcess thyroid hormone — weight loss, palpitations, tremor, heat intolerance, anxiety and diarrhoea. Graves' disease is the commonest cause; thyroid storm is a life-threatening emergency.

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👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Levothyroxine (LT4)

📈 Subclinical, pregnancy & myxoedema coma

📚 References

More protocols

👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Levothyroxine (LT4)

📈 Subclinical, pregnancy & myxoedema coma

📚 References

More protocols

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Subclinical, pregnancy & myxoedema coma

References

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Subclinical, pregnancy & myxoedema coma

References