Select the hormone which acts on mammary glands and stimulates the formation of alveoli?

Options

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

Answer

To solve the question of which hormone acts on mammary glands and stimulates the formation of alveoli, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of Mammary Glands**:
- Mammary glands are responsible for producing milk after childbirth to nourish the newborn. They consist of structures called alveoli, where milk is synthesized and secreted.

2. **Identify the Hormones Involved**:
- The question asks for a hormone that stimulates the formation of alveoli in the mammary glands. The relevant hormones to consider are estrogen, prolactin, progesterone, and oxytocin.

3. **Evaluate Each Hormone**:
- **Estrogen**: Primarily involved in the development of female secondary sexual characteristics and the menstrual cycle. It does not play a significant role in the formation of alveoli.
- **Prolactin**: Responsible for milk production after childbirth but does not stimulate the formation of alveoli.
- **Progesterone**: Plays a crucial role in the development of the mammary glands, particularly in stimulating the formation of alveoli and the branching of ducts necessary for lactation.
- **Oxytocin**: Involved in the ejection of milk from the mammary glands but does not influence the formation of alveoli.

4. **Select the Correct Hormone**:
- Based on the evaluation, progesterone is the hormone that stimulates the formation of alveoli in the mammary glands. It promotes the extensive side branching and alveologenesis necessary for a lactation-competent gland.

5. **Conclusion**:
- The correct answer to the question is **progesterone**.

### Final Answer:
**Progesterone** is the hormone that acts on mammary glands and stimulates the formation of alveoli.