Which one of the following causes mammary glands to enlarge at puberty

Options

A. Testosterone
B. Progesterone
C. Estrogen
D. Oxytocin.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks which hormone causes the enlargement of mammary glands at puberty.

2. **Analyzing the Options:**
- **A. Testosterone:** This is a male sex hormone responsible for male characteristics and sperm formation, not mammary gland enlargement.
- **B. Progesterone:** This hormone is involved in supporting pregnancy and milk secretion but does not primarily cause mammary gland enlargement at puberty.
- **C. Estrogen:** This hormone is crucial for the development of female secondary sexual characteristics and does play a role in mammary gland development.
- **D. Oxytocin:** This hormone is released by the pituitary gland and is involved in various reproductive functions, including the stimulation of mammary gland growth.

3. **Identifying the Correct Hormone:**
Among the options, estrogen is known to stimulate the growth and development of mammary glands during puberty. Oxytocin, while important for milk ejection during lactation, is not the primary hormone responsible for mammary gland enlargement at puberty.

4. **Conclusion:**
The correct answer is **C. Estrogen**, as it is the hormone that primarily causes the enlargement of mammary glands at puberty.