Which of the following is not a symptom of hypothyroidism ?

Options

A. Oedema
B. Lethargy
C. Rise in blood urea
D. Mental retardation

Answer

To determine which of the following is not a symptom of hypothyroidism, we need to analyze the options provided:

1. **Edema**
2. **Lethargy**
3. **Rise in blood urea**
4. **Mental retardation**

### Step-by-Step Solution:

**Step 1: Understand Hypothyroidism**
- Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones. This can lead to various symptoms affecting metabolism and overall health.

**Step 2: Analyze Each Option**
- **Edema**: This refers to swelling caused by excess fluid trapped in the body's tissues. It can be a symptom of hypothyroidism due to water retention.

- **Lethargy**: This is a state of fatigue or lack of energy. It is a common symptom of hypothyroidism as the body's metabolism slows down.

- **Rise in blood urea**: Urea is produced in the liver and is a waste product that is filtered out of the blood by the kidneys. An increase in blood urea levels is typically related to kidney function rather than thyroid function.

- **Mental retardation**: In infants, severe hypothyroidism can lead to developmental delays and cognitive impairments, often referred to as mental retardation.

**Step 3: Identify the Correct Answer**
- After analyzing the options, the rise in blood urea is not a symptom of hypothyroidism. It is more related to kidney function and not directly associated with the thyroid gland.

### Conclusion
The correct answer is **rise in blood urea** as it is not a symptom of hypothyroidism.