Which is not a function of thyroid hormone

Options

A. Regulation of basal metabolic rate
B. Controls metabolism of carbohydrates, proteins and fats
C. Maintains water and electrolyte balance
D. Regulates the diurnal rhythm.

Answer

To determine which option is not a function of thyroid hormone, we can analyze each of the provided functions:

1. **Regulation of Basal Metabolic Rate (BMR)**:
- Thyroid hormones, particularly thyroxine (T4), play a crucial role in regulating the BMR. They increase the metabolic rate of cells, leading to an increase in oxygen consumption and energy expenditure. This function is indeed associated with thyroid hormones.

2. **Control Metabolism of Carbohydrates, Proteins, and Fats**:
- Thyroid hormones are involved in the metabolism of carbohydrates, proteins, and fats. They help in the breakdown of these macromolecules to release energy and maintain metabolic balance. This is also a function of thyroid hormones.

3. **Maintains Water and Electrolyte Balance**:
- While thyroid hormones have various metabolic roles, the maintenance of water and electrolyte balance is primarily the function of calcitonin, which is also produced by the thyroid gland but is not a thyroid hormone in the same sense as T3 and T4. Calcitonin helps regulate calcium levels in the blood, but it does not directly regulate water and electrolyte balance.

4. **Regulation of Diurnal Rhythm**:
- The regulation of the sleep-wake cycle, or diurnal rhythm, is primarily controlled by the hormone melatonin, which is produced by the pineal gland. This function is not associated with thyroid hormones.

Based on this analysis, the option that is not a function of thyroid hormone is:

**Answer: Regulation of Diurnal Rhythm (Option 4)**