Endocrinology Practice Questions

Correct Answer: A

Rationale: Step-by-step rationale for why answer A is correct: 1. Oxytocin is synthesized in the hypothalamus and released into the bloodstream. 2. In the plasma, oxytocin binds to neurophysin, a carrier protein. 3. This binding helps stabilize oxytocin and regulate its release and distribution. 4. Therefore, choice A is correct as oxytocin is bound to neurophysin in plasma. Summary: - Choice B is incorrect as oxytocin stimulates milk ejection, not inhibits milk production. - Choice C is incorrect as oxytocin promotes myometrial contraction during labor. - Choice D is incorrect as oxytocin can enhance sperm motility, not inhibit it.

Correct Answer: C

Rationale: The correct answer is C: Oxytocin. The anterior pituitary gland produces several hormones, including adrenocorticotropic hormone (A), growth hormone (B), and thyroid-stimulating hormone (D). Oxytocin is actually produced by the posterior pituitary gland, not the anterior pituitary. Oxytocin is responsible for uterine contractions during childbirth and milk ejection during breastfeeding. Therefore, C is the correct answer as it is not produced by the anterior pituitary unlike the other hormones mentioned.

Correct Answer: C

Rationale: Step-by-step rationale for why choice C is correct: 1. Growth hormone stimulates increased production of insulin-like growth factor 1 (IGF-1). 2. In acromegaly, there is excessive production of growth hormone. 3. Excess growth hormone leads to elevated levels of IGF-1. 4. IGF-1 is primarily produced in the liver in response to growth hormone stimulation. 5. Therefore, increased levels of growth hormone in acromegaly stimulate increased production of IGF-1 from the liver. Summary: - Choice A is incorrect because vasopressin is not produced from the adrenal glands in response to growth hormone. - Choice B is incorrect because vasopressin is not produced from the liver in response to growth hormone. - Choice D is incorrect because IGF-1 is mainly produced in the liver, not from the adrenal glands, in response to growth hormone.

Correct Answer: B

Rationale: Correct Answer: B (Rheumatic carditis) Rationale: 1. Rheumatic carditis is a heart condition, which may lead to a decreased cardiac output and subsequently a lower pulse rate during sleep. 2. Anxiety neurosis can lead to increased sympathetic activity, causing an elevated pulse rate during sleep. 3. Pulmonary tuberculosis can cause systemic inflammation and increased metabolic demand, resulting in an elevated pulse rate during sleep. 4. Atropine, a parasympatholytic drug, inhibits the action of the parasympathetic nervous system, leading to an increased pulse rate.

Correct Answer: B

Rationale: Excess prolactin causes gynaecomastia due to its stimulatory effect on breast tissue growth in males. Prolactin inhibits the release of testosterone, leading to an imbalance in sex hormones and breast tissue development. Acromegaly is caused by excess growth hormone, not prolactin. Early menopause is unrelated to prolactin levels. Anaemia is typically not associated with prolactin excess. Thus, gynaecomastia is the most appropriate outcome of excess prolactin.