**Question:** All the following are the effects of oestrogen, EXCEPT:

A. Increases red blood cell production
B. Inhibits bone resorption
C. Stimulates breast development in infants
D. Increases appetite

**Core Concept:** Oestrogen is a sex hormone primarily produced by the ovaries in women and testes in men. It plays a crucial role in female reproductive system development, maintenance, and function. Oestrogen has various physiological effects, including:

- Increases red blood cell production (A)
- Inhibits bone resorption (B)
- Stimulates breast development in infants (C)

**Why the Correct Answer is Right:**

D. Increases appetite is not a direct effect of oestrogen. Although oestrogen does have indirect effects on food intake, it is primarily associated with the hormone leptin, which inhibits appetite. Oestrogen can indirectly increase appetite by promoting lipogenesis and fat storage, leading to increased body mass index (BMI) and potentially food intake.

**Why Each Wrong Option is Incorrect:**

A. Increases red blood cell production: While oestrogen indirectly affects haematopoiesis, it does not directly increase red blood cell production. Oestrogen promotes erythropoiesis, but the increase in red blood cell production is mainly due to increased response to erythropoietin.

B. Inhibits bone resorption: Oestrogen plays a crucial role in maintaining bone density by inhibiting bone resorption, which is the process of bone tissue breakdown. This effect is mediated through oestrogen's interaction with osteoclasts, the cells responsible for bone resorption.

C. Stimulates breast development in infants: Oestrogen is essential for breast development during pregnancy and lactation, as it promotes mammary gland development in infants.

**Clinical Pearl:** Oestrogen and progesterone are the primary hormones involved in maintaining pregnancy. Oestrogen stimulates uterine growth and prepares the uterus for implantation, while progesterone maintains the uterine lining and supports placental development.

**Correct Answer:**

D. Increases appetite (Option D)

**Explanation:** Increased appetite is primarily mediated by leptin, a hormone produced by adipose tissue, rather than oestrogen. Leptin suppresses appetite, while oestrogen affects appetite indirectly by promoting fat storage and body weight gain, which can lead to increased food intake.