## **Core Concept**
Hypothyroidism in infancy, also known as congenital hypothyroidism, results from a deficiency of thyroid hormone production. This condition can lead to growth and developmental delays if not promptly treated. The features often include physical and neurological abnormalities.

## **Why the Correct Answer is Right**
The correct answer, which isn't specified here, typically relates to a feature that is not commonly associated with hypothyroidism in infancy. Common features include large tongue (macroglossia), umbilical hernia, dry skin, constipation, and delayed milestones. The correct answer likely highlights an exception or a less characteristic feature.

## **Why Each Wrong Option is Incorrect**
- **Option A:** If this option describes a common feature like macroglossia, it would be incorrect to say it's not a feature.
- **Option B:** Similarly, if this option mentions another common feature such as umbilical hernia or dry skin, it would be wrong to exclude it.
- **Option D:** This option would also describe a characteristic feature, making it an incorrect choice if it indeed represents a feature of hypothyroidism in infancy.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that early detection and treatment of congenital hypothyroidism are crucial for preventing intellectual disability and growth retardation. Screening programs are in place in many countries to detect this condition early, often through heel prick blood tests.

## **Correct Answer: D. Large head.**
However, note that large head (macrocephaly) isn't typically listed as a feature; instead, features often include a large tongue and a delay in bone age leading to a relatively large head compared to the body but still proportionate or within normal limits for age. Untreated congenital hypothyroidism more commonly presents with a smaller head circumference (microcephaly) or proportionate growth issues rather than macrocephaly.