Hypothalamo-Pituitary Axis and Neuroendocrine Integration MCQs

Physiology · 61 free questions with answers & explanations.

  1. A 28-year-old woman presents with galactorrhea, secondary amenorrhea, and a serum prolactin of 180 ng/mL. MRI shows a 6mm pituitary lesion. The mechanism by which a microprolactinoma causes amenorrhea is best explained as:
  2. The parvocellular neurons of the paraventricular nucleus (PVN) that regulate the HPA axis project to the median eminence and release CRH into the hypophyseal portal blood. Which physiological condition would MOST potently stimulate these neurons?
  3. A 45-year-old man undergoes testing for suspected acromegaly. Paradoxical GH secretion in response to oral glucose load (GH rises rather than falls) is found. The mechanism of this paradoxical response is:
  4. Kisspeptin (KP) neurons of the hypothalamic arcuate nucleus are critical for the pubertal activation of the GnRH pulse generator. Which statement best describes the neuroendocrine integration involving kisspeptin?
  5. A patient with central diabetes insipidus receives a low dose of exogenous ADH. The primary renal tubular location where ADH exerts its major antidiuretic effect, and the intracellular mediator involved, are:
  6. A 32-year-old woman presents with galactorrhoea, amenorrhoea and serum prolactin of 180 ng/mL. MRI shows a 6 mm pituitary lesion. Which physiological mechanism best explains why a dopamine agonist will lower prolactin?
  7. The 'short-loop' negative feedback in the hypothalamo-pituitary axis refers to:
  8. During the preovulatory LH surge, which shift in gonadotroph physiology allows GnRH to STIMULATE rather than desensitise LH release?
  9. Magnocellular neurons of the hypothalamus synthesise ADH and oxytocin as prohormones. Which neurophysiological feature characterises their secretion into the systemic circulation?
  10. Growth hormone secretion is LOWEST during which physiological state?
  11. A 28-year-old woman has galactorrhea and amenorrhea. Her serum prolactin is markedly elevated. The neuroendocrine mechanism most directly responsible for hyperprolactinemia in a prolactin-secreting pituitary adenoma (prolactinoma) is:
  12. The pulsatile rather than continuous secretion of GnRH is essential for maintaining gonadotropin secretion. If GnRH is administered as a continuous infusion rather than pulsatile delivery, the expected pituitary response is:
  13. The CRH-ACTH-cortisol axis demonstrates a circadian rhythm with peak cortisol levels at approximately 8 AM. The neuroendocrine driver generating this rhythm is:
  14. In central diabetes insipidus following pituitary surgery, the 'triple phase' response of urine output occurs because:
  15. Kisspeptin (Kiss1) neurons in the hypothalamus are critical regulators of the reproductive axis. In pubertal onset, the primary change in kisspeptin signaling is:
  16. A 32-year-old woman presents with galactorrhea, secondary amenorrhea, and a serum prolactin of 180 ng/mL. MRI reveals a 6 mm pituitary adenoma. Which physiological mechanism is responsible for the amenorrhea in hyperprolactinemia?
  17. A researcher ablates the hypothalamic arcuate nucleus in a rat. Which endocrine axis would show the MOST profound and sustained disruption?
  18. During a prolonged fast of 48 hours, the hypothalamic-pituitary-thyroid axis undergoes an adaptive change. Which statement BEST describes this adaptation?
  19. A patient with a craniopharyngioma involving the hypothalamic-pituitary stalk develops diabetes insipidus. The posterior pituitary is intact on MRI. Which mechanism explains the DI?
  20. The hypothalamic ventromedial nucleus (VMH) is considered the 'satiety center.' Which neuroendocrine signal acts DIRECTLY on VMH neurons to enhance satiety signaling after a meal?
  21. A 35-year-old man with a pituitary macroadenoma has a serum prolactin of 3800 ng/mL. He undergoes venous sampling from both inferior petrosal sinuses and peripheral blood during CRH stimulation. The central:peripheral prolactin gradient is 2.0. What is the significance of this finding?
  22. Which of the following CORRECTLY describes the feedback control of the hypothalamo-pituitary-thyroid axis that distinguishes tertiary from secondary hypothyroidism?
  23. A 30-year-old athlete's serum GH level is measured at 8 AM after an overnight fast and is found to be undetectable (<0.05 ng/mL). Her IGF-1 is within the normal range. What is the correct interpretation?
  24. The hypothalamic neurotransmitter kisspeptin plays a central role in puberty and reproduction. Which receptor does kisspeptin act on, and what is its primary effect on GnRH neurons?
  25. A 28-year-old woman with galactorrhea and secondary amenorrhea has serum prolactin of 180 ng/mL. MRI shows a 6 mm microadenoma. Which hypothalamic mechanism is MOST directly responsible for the elevated prolactin?
  26. The pulsatile nature of GnRH release is critical for normal gonadotropin secretion. If GnRH is given as a continuous infusion rather than in pulses, which of the following changes occurs?
  27. A patient undergoes transphenoidal resection of a large pituitary macroadenoma. Postoperatively he develops polyuria (urine output 6 L/day) with dilute urine (specific gravity 1.002) and hypernatremia. Which of the following correctly describes the hormonal defect?
  28. The corticotropin-releasing hormone (CRH) test is used to distinguish Cushing's disease from ectopic ACTH syndrome. In Cushing's disease, IV CRH administration causes:
  29. Which of the following best explains why high-dose dexamethasone (8 mg overnight) suppresses urinary free cortisol in Cushing's disease but NOT in ectopic ACTH syndrome?
  30. A 28-year-old woman presents with amenorrhoea, galactorrhoea, and a serum prolactin of 180 ng/mL. MRI reveals a 6 mm pituitary microadenoma. Which of the following best explains the physiological mechanism by which hypothalamic dopamine normally suppresses prolactin secretion?
  31. A patient with central diabetes insipidus is given DDAVP and responds with concentrated urine. The V2 receptor activated by DDAVP in principal cells of the collecting duct operates through which intracellular signalling cascade to insert aquaporin-2 (AQP2) into the apical membrane?
  32. Pulsatile GnRH secretion at 90-minute intervals drives normal LH secretion. In a GnRH analogue protocol for IVF, continuous GnRH agonist administration is used for pituitary down-regulation. What is the primary mechanism of this paradoxical suppression?
  33. In evaluating a patient with suspected acromegaly, which dynamic test provides the most reliable physiological confirmation, and what is the expected result in an affected individual?
  34. The hypothalamic melanocortin system plays a central role in energy homeostasis. Which of the following correctly describes how leptin and NPY/AgRP neurons interact within the arcuate nucleus to regulate food intake?
  35. A 28-year-old woman presents with galactorrhea and secondary amenorrhea. Serum prolactin is 95 ng/mL. Which of the following best explains why dopamine normally suppresses prolactin secretion?
  36. During stress, CRH release from the hypothalamic paraventricular nucleus triggers ACTH secretion. Which negative feedback mechanism most rapidly terminates an acute CRH/ACTH surge?
  37. A male patient with a craniopharyngioma involving the hypothalamus develops diabetes insipidus, central hypogonadism, and hypothyroidism. The TSH level is low-normal and free T4 is low. This pattern of central hypothyroidism is due to:
  38. The pulsatile GnRH secretion from the hypothalamus is essential for normal LH/FSH release. Continuous (non-pulsatile) administration of a GnRH agonist causes:
  39. Osmoreceptors controlling ADH (vasopressin) secretion are located primarily in which hypothalamic nucleus, and what is the osmolality threshold that triggers ADH release?
  40. A 35-year-old woman presents with galactorrhoea, amenorrhoea, and a serum prolactin of 180 ng/mL. MRI shows a 6 mm pituitary microadenoma. Prolactin secretion from lactotrophs is tonically inhibited by which hypothalamic mediator?
  41. ADH (vasopressin) is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus and stored in the posterior pituitary. Its primary stimulus for secretion is:
  42. Pulsatile GnRH secretion from the hypothalamus is essential for normal gonadotropin secretion. In a patient treated with a continuous (non-pulsatile) GnRH agonist for prostate cancer, the long-term effect on LH and FSH secretion is:
  43. In the hypothalamic-pituitary-adrenal (HPA) axis, the CRH-ACTH-cortisol system exhibits a circadian rhythm. The peak cortisol secretion normally occurs at approximately:
  44. A child with a craniopharyngioma compressing the hypothalamus develops diabetes insipidus, growth retardation, and obesity. The obesity results primarily from damage to which hypothalamic nucleus?
  45. A 28-year-old woman presents with galactorrhea and secondary amenorrhea. MRI shows a 6 mm pituitary microadenoma. Her serum prolactin is 180 ng/mL. Which hypothalamic factor is responsible for the tonic inhibition of prolactin secretion under normal circumstances?
  46. In the hypothalamo-pituitary portal system, which statement best describes the functional significance of the short portal vessels connecting the posterior pituitary to the anterior pituitary?
  47. A patient with a craniopharyngioma has pan-hypopituitarism. Which hormonal axis will clinically manifest EARLIEST and most prominently after complete hypophyseal stalk section?
  48. GnRH is secreted in a pulsatile fashion from the hypothalamus. A patient is being treated with continuous (non-pulsatile) GnRH administration. What effect is expected on LH and FSH?
  49. Which of the following correctly describes the mechanism by which somatostatin inhibits GH release from the anterior pituitary?
  50. A 35-year-old man with acromegaly undergoes an oral glucose tolerance test (75 g glucose). Which GH pattern is DIAGNOSTIC of acromegaly?
  51. A 28-year-old woman presents with amenorrhea and galactorrhea. MRI reveals a 4 mm pituitary microadenoma. Which of the following best explains why elevated prolactin causes amenorrhea?
  52. Which portal vessel characteristic is unique to the hypothalamo-hypophyseal portal system compared to other portal systems in the body?
  53. A male patient with a craniopharyngioma compressing the pituitary stalk shows paradoxically elevated serum prolactin. Which mechanism best explains this finding?
  54. Kisspeptin neurons in the arcuate nucleus fire in synchrony with GnRH pulses. What is the principal role of kisspeptin in the reproductive axis?
  55. A patient undergoes an insulin tolerance test (ITT). Despite adequate hypoglycemia (glucose < 2.2 mmol/L), his cortisol rises to only 380 nmol/L (normal > 500 nmol/L). Which level of the hypothalamo-pituitary-adrenal axis is most likely impaired?
  56. The hypothalamic peptide that exerts a direct inhibitory effect on pituitary GH secretion, while also suppressing TSH, glucagon, and pancreatic exocrine secretion, is:
  57. A patient on long-term dopamine agonist therapy for Parkinson's disease develops amenorrhoea and galactorrhoea. The mechanism involves dopamine's role as:
  58. The hypothalamic nucleus responsible for integrating circadian rhythms and acting as the 'master biological clock' is the:
  59. GnRH is released in a pulsatile fashion. What is the physiological consequence of continuous (non-pulsatile) GnRH administration as used in the treatment of precocious puberty?
  60. ADH (vasopressin) synthesized in the hypothalamus is transported to the posterior pituitary via:
  61. A 30-year-old woman with panhypopituitarism after pituitary apoplexy requires hormone replacement. The correct physiological order of hormone supplementation priority (most critical first) is:
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