# Iodine, Zinc and Micronutrient Deficiency Disorders

> Iodine and zinc deficiency disorders for NEET-PG Medicine: goitre, cretinism, iodised salt, acrodermatitis enteropathica and zinc with ORS in children.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/iodine-deficiency-and-micronutrient-disorders
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Park's Textbook of Preventive and Social Medicine; Harrison's Principles of Internal Medicine; Ghai Essential Pediatrics
- How to cite: "Iodine, Zinc and Micronutrient Deficiency Disorders", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/iodine-deficiency-and-micronutrient-disorders

## Direct answer

Iodine deficiency disorders range from goitre and hypothyroidism to cretinism, the irreversible neurological syndrome produced when deficiency occurs in fetal life and infancy. Zinc deficiency produces growth failure, impaired immunity and diarrhoea, and in its genetic form acrodermatitis enteropathica. Universal salt iodisation and zinc with oral rehydration are the central preventive measures in India.

## What you must remember

- **Goitre:** diffuse enlargement of the thyroid from raised TSH stimulating a short-of-iodine gland; mild deficiency is often euthyroid, while severe deficiency causes hypothyroidism.
- **Cretinism:** the endemic neurological form, with intellectual disability, deaf-mutism and spastic diplegia, caused by deficiency in fetal life and early infancy.
- **Pregnancy:** iodine deficiency raises miscarriage, stillbirth and fetal thyroid hormone shortfall, so supplementation is advised in endemic areas.
- **Prevention:** universal salt iodisation is the mainstay; excess iodine also causes goitre and hypothyroidism through the Wolff-Chaikoff effect.
- **Zinc deficiency signs:** growth failure, hypogonadism, impaired taste, poor wound healing, night blindness and recurrent infections.
- **Acrodermatitis enteropathica:** an autosomal recessive defect in zinc absorption causing periorificial and acral dermatitis, alopecia, diarrhoea and irritability, which responds to oral zinc.
- **Acquired zinc deficiency:** malabsorption, prolonged parenteral nutrition without zinc, chronic alcohol use and sickle cell disease can mimic acrodermatitis.
- **Indian programme:** children with diarrhoea receive zinc with oral rehydration, usually for 14 days, to shorten the episode and reduce recurrence.

## Worked examples: a goitre before pregnancy and a rash in infancy

A 26-year-old woman from a hilly district has a diffusely enlarged, non-tender thyroid and mild fatigue. TSH is mildly raised with normal free T4, urinary iodine is low, and her household uses non-iodised salt.

1. **Confirm iodine deficiency:** Measure urinary iodine and check thyroid antibodies, since autoimmune thyroiditis can produce a similar goitre.
2. **Image the gland:** Ultrasound records any nodularity, and thyroid function is repeated.
3. **Protect the pregnancy:** Because she plans pregnancy, the greatest concern is the fetus, which depends on maternal thyroxine in early development.
4. **Treat and supplement:** Management is iodised salt for the household, iodine supplementation in pregnancy as advised by her physician, and thyroid replacement if hypothyroidism is present. Her newborn should be screened for congenital hypothyroidism.
5. **Compare the infant:** A six-month-old infant has cracked skin around the mouth and anus, diarrhoea and poor weight gain. Serum zinc is low, and the infant responds to oral zinc within days.
6. **Name the lesson:** Acrodermatitis enteropathica is a skin and growth syndrome that mimics a nutritional or infective picture, and it is treated with zinc rather than antibiotics.

## Where the question tests cause, not consequence

Examiners test the cause behind a finding, and the same few confusions recur.

- **Trap:** equating goitre with hypothyroidism. — **Correct:** goitre is a feature of iodine deficiency, not its definition, and the gland can be enlarged with normal hormone levels.
- **Trap:** treating cretinism after birth. — **Correct:** cretinism is tested for prevention, and the right answer is iodine supplementation in pregnancy and universal salt iodisation.
- **Trap:** reading a low serum zinc as proof of deficiency. — **Correct:** serum zinc falls with infection and inflammation, so a low value must be read with the clinical picture.
- **Trap:** confusing acrodermatitis enteropathica with biotin deficiency or candidiasis. — **Correct:** the decisive clue is the response to oral zinc.

## Frequently asked questions

### What is the leading preventable cause of brain damage linked to iodine?

Iodine deficiency in fetal life and early infancy is the world's leading preventable cause of brain damage, and cretinism is its most severe neurological form. Universal salt iodisation and iodine supplementation in pregnancy are the main preventive measures.

### Why is goitre not the same as hypothyroidism?

Goitre is enlargement of the thyroid gland and is not the same as hypothyroidism, since the gland may be enlarged while thyroid hormone levels remain normal. In iodine deficiency, goitre develops as TSH stimulates the gland, and hypothyroidism appears only with more severe deficiency.

### What does the Wolff-Chaikoff effect describe?

The Wolff-Chaikoff effect describes the temporary block of thyroid hormone synthesis in response to excess iodine, which can cause goitre and hypothyroidism. It explains why iodine excess is harmful and why supplements should be dosed rather than taken without limit.

### Why is serum zinc unreliable in diagnosing zinc deficiency?

Serum zinc falls during infection and inflammation, so a low value does not always mean deficiency and a normal value does not exclude it. Zinc status is judged with the clinical picture, diet history and response to supplementation alongside the serum level.

### Which conditions does acrodermatitis enteropathica resemble?

Acrodermatitis enteropathica resembles candidiasis and biotin deficiency, which share its periorificial rash and diarrhoea. Its response to oral zinc and the low serum zinc level separate it from those conditions in practice.