The birth or the milk ejecting hormone ; oxytocin

Options

A. is secreted by anterior pituitary
B. stimulates growth of mammary glands
C. stimulates pituitary to secrete vasopressin
D. causes strong uterine contractions during parturition

Explanation

**Step-by-Step Solution:**

1. **Understanding Oxytocin**: Oxytocin is a hormone that plays a crucial role in childbirth and lactation. It is often referred to as the "birth hormone" because it stimulates uterine contractions during labor and is also known as the "milk ejection hormone" as it helps in the ejection of milk during breastfeeding.

2. **Identifying the Source**: Oxytocin is produced in the hypothalamus and is secreted by the posterior pituitary gland (also known as neurohypophysis). It is important to note that it is not secreted by the anterior pituitary.

3. **Evaluating the Options**:
- **Option 1**: States that oxytocin is secreted by the anterior pituitary. This is incorrect as oxytocin is secreted by the posterior pituitary.
- **Option 2**: Claims that it stimulates the growth of mammary glands. This is also incorrect; the growth of mammary glands is primarily influenced by estrogen.
- **Option 3**: Suggests that oxytocin stimulates the pituitary to secrete vasopressin. This is incorrect as well; while both hormones are secreted by the posterior pituitary, oxytocin does not stimulate the secretion of vasopressin.
- **Option 4**: States that oxytocin causes strong uterine contractions during parturition. This is correct, as oxytocin is responsible for stimulating the myometrium (the muscular layer of the uterus) to contract during childbirth.

4. **Conclusion**: Based on the evaluation of the options, the correct answer is that oxytocin causes strong uterine contractions during parturition.

**Final Answer**: Oxytocin is the hormone that causes strong uterine contractions during parturition.

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