Endocrinology Exam Questions and Answers

Correct Answer: C

Rationale: Cortisol secretion is directly stimulated by adrenocorticotropic hormone (ACTH), which is produced and released by the anterior pituitary gland in response to corticotropin-releasing hormone (CRH) from the hypothalamus. ACTH acts on the adrenal cortex to stimulate the production and release of cortisol. Aldosterone is another hormone produced by the adrenal cortex, but it is not directly involved in the stimulation of cortisol secretion. Prolactin is a hormone produced by the pituitary gland that plays a role in lactation, not cortisol secretion. High blood potassium levels can stimulate aldosterone secretion but do not directly stimulate cortisol secretion.

Correct Answer: C

Rationale: Oxytocin is a hormone that is produced in both males and females. In females, oxytocin plays a crucial role in various physiological processes, notably during labor and childbirth. Oxytocin acts on the smooth muscles of the uterus, causing them to contract during labor (parturition) and helps in the ejection of milk during breastfeeding. This hormone is primarily synthesized in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus and stored in the posterior pituitary gland before being released into the bloodstream. Overall, oxytocin's main function is to stimulate smooth muscle contraction in the uterus and the mammary glands.

Correct Answer: D

Rationale: The renin-angiotensin-aldosterone axis does not involve the hypothalamus or pituitary gland; instead, it primarily involves the kidneys and the renin-secreting cells. In this axis, renin is released in response to low blood pressure, leading to the formation of angiotensin II and the subsequent release of aldosterone from the adrenal glands. Feedback mechanisms for this axis primarily involve the regulation of renin release based on blood pressure rather than involving direct negative feedback from downstream hormones on the hypothalamus or pituitary gland. On the other hand, choices A, B, and C all involve classic examples of hypothalamic-pituitary negative feedback loops where the end hormone suppresses the release of the stimulating hormones at the hypothalamic and pituitary levels.

Correct Answer: D

Rationale: Blood calcium levels are primarily regulated by the actions of parathyroid hormone (PTH) and Vitamin D. Vitamin D plays a crucial role in maintaining calcium balance in the body by promoting the absorption of calcium from the intestines. When blood calcium levels are low, Vitamin D works to increase absorption of calcium to raise the levels back to normal. Therefore, elevated blood calcium levels are commonly associated with excess Vitamin D intake or conditions that increase Vitamin D levels, such as hypervitaminosis D.

Correct Answer: B

Rationale: The earliest changes observed by ophthalmoscope in background retinopathy of diabetes is typically the presence of microaneurysms. These are small dilations of retinal capillaries due to weakening of the vessel walls caused by diabetes-induced damage. Microaneurysms are a hallmark sign of diabetic retinopathy and are often the first visible sign on retinal examination. Other changes in diabetic retinopathy, such as venous dilatation, increased capillary permeability, and arteriovenous shunts, may develop later in the disease process as it progresses.