Asper WHO guidelines, iodine deficiency disorders are endemic in the community when prevalence of goitre in school age children is more than –

**Core Concept**
The World Health Organization (WHO) has established guidelines for assessing iodine deficiency disorders in communities. Iodine deficiency is a significant public health concern, leading to goiter, hypothyroidism, and other thyroid-related complications. The prevalence of goiter in school-age children is a key indicator of iodine deficiency.

**Why the Correct Answer is Right**
According to the WHO guidelines, a goiter prevalence of more than 5% in school-age children is considered a public health problem, indicating endemic iodine deficiency. This threshold is used to identify areas where iodine supplementation programs are necessary to prevent and control iodine deficiency disorders. The prevalence of goiter in school-age children is a sensitive indicator of iodine status, as they are in a critical period of growth and development.

**Why Each Wrong Option is Incorrect**
**Option A:** 1% - This is too low to indicate endemic iodine deficiency, as it may be within the normal range for many populations.
**Option B:** 10% - While this is a higher prevalence, it is still not the threshold used by the WHO to indicate endemic iodine deficiency.
**Option C:** 20% - This is an excessively high prevalence, far beyond the threshold used to indicate endemic iodine deficiency.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the prevalence of goiter in school-age children is a critical indicator of iodine status in a community. Regular monitoring of this population can help identify areas where iodine supplementation programs are necessary to prevent and control iodine deficiency disorders.

**Correct Answer: C. 5%.**