Lactional amenorrhea is due to
**Core Concept**
Lactational amenorrhea is a condition characterized by the cessation of menstrual cycles in women who are breastfeeding. This phenomenon is attributed to the inhibitory effects of prolactin and other hormones on the hypothalamic-pituitary-ovarian axis.
**Why the Correct Answer is Right**
During lactation, the high levels of prolactin stimulate the release of gonadotropin-inhibitory hormone (GnIH) from the hypothalamus, which in turn inhibits the release of gonadotropin-releasing hormone (GnRH) from the anterior pituitary gland. This leads to a decrease in the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), resulting in anovulation and amenorrhea. The suckling stimulus also activates the hypothalamic-pituitary-adrenal (HPA) axis, releasing cortisol, which further contributes to the suppression of gonadotropin secretion.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as lactational amenorrhea is not primarily due to stress or psychological factors.
* **Option B:** This option is incorrect as lactational amenorrhea is not caused by an imbalance of thyroid hormones.
* **Option C:** This option is incorrect as lactational amenorrhea is not directly related to the use of oral contraceptives.
**Clinical Pearl / High-Yield Fact**
Lactational amenorrhea is a reversible condition, and menstrual cycles typically resume when breastfeeding is discontinued or significantly reduced. The World Health Organization (WHO) recommends that lactational amenorrhea be used as a reversible form of contraception, provided that the woman is fully breastfeeding and has not yet had a menstrual cycle since delivery.
**Correct Answer: D. Prolactin-induced inhibition of GnRH release.**