Bone resorption is accelerated by:

Correct Answer: B

Rationale: The correct answer is B: Parathormone. Parathormone stimulates osteoclast activity, which leads to increased bone resorption. Estrogens (choice A) actually inhibit bone resorption. Bisphosphonates (choice C) are used to decrease bone resorption. Calcitonin (choice D) also inhibits bone resorption by blocking osteoclast activity. Therefore, the correct choice is parathormone as it directly accelerates bone resorption by stimulating osteoclasts.

Correct Answer: B

Rationale: The correct answer is B: Rifampicin. Rifampicin is an enzyme inducer that can accelerate the metabolism of oral contraceptives, leading to decreased effectiveness and potential contraceptive failure. It induces hepatic enzymes, increasing the metabolism of estrogen and progestin in oral contraceptives, reducing their efficacy. Isoniazid (A), Cimetidine (C), and Propranolol (D) do not have significant interactions with oral contraceptives.

Correct Answer: B

Rationale: The correct answer is B: Disruption of cyclic menstrual bleeding. Injectable contraceptive depot medroxyprogesterone acetate can cause irregular menstrual bleeding patterns, such as prolonged spotting or amenorrhea. This occurs due to the suppression of ovulation and the thinning of the endometrial lining. Nausea and vomiting (choice A) are less common side effects and usually subside after the initial injections. Venous thrombosis (choice C) and hypertension (choice D) are more associated with combined hormonal contraceptives containing estrogen.

Correct Answer: D

Rationale: The correct answer is D because the progestin component of the combined pill serves multiple purposes. Firstly, it suppresses ovulation by inhibiting the release of an egg from the ovary, preventing pregnancy. Secondly, it helps induce prompt bleeding at the end of the pill course, mimicking a natural menstrual cycle. Lastly, progestin also blocks the increased risk of endometrial carcinoma associated with unopposed estrogen use. Therefore, all of the choices A, B, and C are correct in relation to the purposes served by the progestin component.

Correct Answer: A

Rationale: Step 1: Mifepristone is a progesterone receptor antagonist. Step 2: In the late luteal phase, progesterone levels drop, leading to menstruation. Step 3: By inhibiting progesterone action, mifepristone induces menstruation. Step 4: Therefore, the correct answer is A - induces menstruation. Summary: B is incorrect as mifepristone does not postpone menstruation. C is incorrect as it does not prevent luteolysis but rather triggers it. D is incorrect as mifepristone does not cause decidualization of endometrium.