# Thyroid Disorders

> Thyroid disorders for FMGE: TSH-led interpretation, levothyroxine rules, Graves disease, thyroid storm, pregnancy targets and iodised-salt programme points.

- Canonical URL: https://prepelephant.com/topics/fmge/medicine/thyroid-disorders
- Exam / course: FMGE · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Thyroid Disorders", PrepElephant, https://prepelephant.com/topics/fmge/medicine/thyroid-disorders

## Direct answer

Thyroid assessment in clinical practice begins with the TSH: a high TSH with low free T4 defines primary hypothyroidism, a low TSH with high free T4 defines primary hyperthyroidism, and both normal in the presence of symptoms argues against significant dysfunction. Hypothyroidism is treated with once-daily levothyroxine on an empty stomach, while Graves disease — the commonest cause of hyperthyroidism in young Indian women — is managed with a thionamide course, beta-blockade for symptoms and, in selected cases, radioiodine or surgery. India's iodisation programme under its iodine deficiency disorders control efforts has made simple goitre preventable, though autoimmune disease remains common.

## What you must remember

- Interpretation ladder: TSH first, then free T4; a deranged TSH with normal free T4 is subclinical disease, treated only when the TSH is clearly raised (commonly above 10 mIU per litre), in pregnancy, or when symptoms are convincing.
- Levothyroxine is taken fasting, 45 to 60 minutes before breakfast, at a replacement dose near 1.6 micrograms per kg per day; iron, calcium and proton pump inhibitors interfere with absorption and must be separated.
- Graves disease: diffusely enlarged painless goitre, orbitopathy, pretibial myxoedema and thyroid acropachy; first-line in India is a 12-to-18 month thionamide course (carbimazole or methimazole), with propranolol for symptom control.
- Propylthiouracil is preferred in the first trimester of pregnancy and in thyroid storm; watch thionamides for agranulocytosis — a sore throat on treatment demands an urgent blood count.
- Thyroid storm presents with fever, tachyarrhythmia, agitation or coma and heart failure; treatment combines propylthiouracil, iodine (given at least an hour after the thionamide), beta-blockade, steroids and supportive care.
- Pregnancy raises levothyroxine needs by roughly 30 per cent; the first-trimester TSH target is below 2.5 mIU per litre, and untreated maternal hypothyroidism harms fetal neurodevelopment.
- Subacute (de Quervain) thyroiditis gives a tender goitre with a suppressed TSH, raised inflammatory markers and a poor tracer uptake, contrasting with the high uptake of Graves disease; it resolves with NSAIDs and steroids if needed.

## Common confusion

Candidates confuse primary with central disease: a low TSH with a low free T4 points to pituitary failure, needing further pituitary work-up, not levothyroxine alone. The second trap is the nodular distinction — a toxic multinodular goitre or a hot nodule is not Graves disease and responds poorly to thionamides alone, favouring radioiodine. Finally, remember that a tender gland means thyroiditis, where antithyroid drugs are useless because the hyperthyroidism is destructive release, not synthesis.

## Exam-focused takeaway

FMGE thyroid questions are interpret-and-prescribe: the TSH–T4 pattern names the disease, the empty-stomach levothyroxine rule answers dosing questions, and the young woman with goitre, eye signs and tremor is Graves disease treated with a thionamide. Learn the pregnancy target and the 30 per cent dose increase, the propylthiouracil-first rule in the first trimester, and the sore-throat agranulocytosis alarm. A fever-plus-arrhythmia stem is thyroid storm, where sequence matters: block synthesis, then iodine, then supportive therapy.

## Frequently asked questions

### How is levothyroxine taken correctly?

Fasting, 45 to 60 minutes before breakfast, with iron and calcium supplements separated by several hours because they block absorption.

### What distinguishes Graves disease from other causes of hyperthyroidism?

Diffuse goitre with orbitopathy, pretibial myxoedema, TSH-receptor antibodies and a high radioiodine uptake, against the poor uptake of destructive thyroiditis.

### Which antithyroid drug is used in the first trimester?

Propylthiouracil, because carbimazole and methimazole carry teratogenic risk; most women can switch back later in pregnancy.

### What is the first-trimester TSH target in pregnancy?

Below about 2.5 mIU per litre, achieved by increasing the pre-pregnancy levothyroxine dose as soon as pregnancy is confirmed.

### What marks thyroid storm?

Fever, marked tachyarrhythmia, agitation or coma with heart failure — treated with propylthiouracil, then iodine, beta-blockade and steroids.