Endocrine regulation Practice Questions
23 free Endocrine regulation practice questions for the USMLE Step 1. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following is the most common mechanism by which hormone secretion is regulated in the endocrine system?
- A Positive feedback from the target gland
- B Negative feedback from the target gland
- C Autocrine stimulation within the same gland
- D Neural conduction along endocrine tissues
Correct answer: Negative feedback from the target gland
Negative feedback from the target gland is the predominant mechanism by which hormone secretion is regulated: when target-gland hormone levels rise sufficiently, they inhibit further release from the hypothalamus and/or pituitary, maintaining homeostasis.
In the HPA axis, what is the correct sequence of hormone release during a stress response?
- A ACTH → CRH → Cortisol
- B Cortisol → ACTH → CRH
- C CRH → ACTH → Cortisol
- D CRH → Cortisol → ACTH
Correct answer: CRH → ACTH → Cortisol
In the HPA axis, stress triggers hypothalamic release of CRH, which stimulates the anterior pituitary to release ACTH; ACTH then acts on the adrenal cortex to produce cortisol.
Elevated circulating cortisol levels will most directly inhibit which of the following?
- A Renin-angiotensin-aldosterone system (RAAS) activation
- B Thyroid-stimulating hormone (TSH) secretion
- C Corticotropin-releasing hormone (CRH) and ACTH release
- D Insulin secretion from pancreatic beta cells
Correct answer: Corticotropin-releasing hormone (CRH) and ACTH release
Cortisol exerts negative feedback on both the hypothalamus and the anterior pituitary, reducing CRH and ACTH secretion to regulate HPA axis activity.
Which type of stimulus refers to regulation of an endocrine gland by changes in blood ion concentration or other non-hormonal blood chemicals?
- A Neural stimulus
- B Hormonal stimulus
- C Humoral stimulus
- D Autocrine stimulus
Correct answer: Humoral stimulus
A humoral stimulus refers to the release of hormones in response to changing levels of ions or nutrients in the blood (e.g., calcium, glucose, osmolarity).
Which anterior pituitary hormone is directly stimulated by (TRH)?
- A ACTH
- B TSH
- C GH
- D Prolactin
Correct answer: TSH
TRH from the hypothalamus stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH), which in turn acts on the thyroid gland.
If circulating free thyroid hormone (T3/T4) levels rise, what happens to TRH and TSH secretion under normal physiology?
- A Both TRH and TSH increase
- B TRH increases, TSH decreases
- C Both TRH and TSH decrease
- D TRH decreases, TSH increases
Correct answer: Both TRH and TSH decrease
Elevated levels of free T3/T4 exert negative feedback on both the hypothalamus (decreasing TRH) and the anterior pituitary (decreasing TSH), reducing further thyroid hormone secretion.
Which of the following best describes a ‘tropic’ hormone?
- A A hormone that acts on the same gland that secreted it
- B A hormone that regulates metabolism directly in peripheral tissues
- C A hormone that stimulates another endocrine gland to release a hormone
- D A peptide hormone derived from cholesterol
Correct answer: A hormone that stimulates another endocrine gland to release a hormone
Tropic hormones are those secreted by one endocrine gland (e.g., pituitary) that stimulate another endocrine gland to release its hormone (e.g., TSH → thyroid gland).
In the regulation of the (HPG axis), continuous (non-pulsatile) administration of (GnRH) leads to which of the following outcomes?
- A Increased LH and FSH release from pituitary
- B Decreased LH and FSH release from pituitary
- C Increased sex steroid production from gonads
- D No change in gonadal function
Correct answer: Decreased LH and FSH release from pituitary
Continuous (non-pulsatile) GnRH leads to downregulation of GnRH receptors in the pituitary and paradoxically reduces LH and FSH release, suppressing gonadal function — a principle used clinically for GnRH agonist therapy.
Which of the following hormones is primarily regulated by a humoral stimulus related to blood osmolarity rather than hormonal feedback?
- A TSH
- B ACTH
- C ADH
- D FSH
Correct answer: ADH
ADH (vasopressin) release is regulated by osmoreceptors in the hypothalamus sensing changes in blood osmolarity (a humoral stimulus), prompting water reabsorption to correct osmolarity.
Which of the following pairs appropriately illustrates a hormone and its primary peripheral effect?
- A TSH → increased insulin release
- B ACTH → increased cortisol secretion
- C GnRH → increased thyroid hormone production
- D ADH → increased glucagon secretion
Correct answer: ACTH → increased cortisol secretion
ACTH stimulates the adrenal cortex to secrete cortisol (a glucocorticoid), which is the primary peripheral effect in the HPA axis response.
The secretion of hormones in many endocrine axes is pulsatile or circadian rather than constant. What is a key advantage of such rhythmic secretion?
- A It ensures constant maximal receptor activation
- B It prevents receptor down-regulation over time
- C It eliminates negative feedback suppression
- D It causes permanent elevation of hormone levels
Correct answer: It prevents receptor down-regulation over time
Pulsatile or circadian secretion avoids continuous receptor stimulation, thereby reducing receptor down-regulation and helping maintain sensitivity of target tissues.
During a prolonged period of high stress, which endocrine axis is most directly responsible for maintaining elevated glucocorticoid levels?
- A HPG axis
- B Thyroid axis
- C HPA axis
- D Somatotropic axis
Correct answer: HPA axis
The HPA axis governs the stress response by increasing CRH, ACTH, and ultimately cortisol (a glucocorticoid), thus sustaining elevated levels during prolonged stress.
Which of the following correctly describes the control of (TSH) secretion under normal physiology?
- A TSH release is stimulated by high circulating T3/T4
- B TSH release is independent of hypothalamic input
- C TSH release increases when circulating T3/T4 levels fall
- D TSH release occurs only in response to neural stimuli
Correct answer: TSH release increases when circulating T3/T4 levels fall
When circulating thyroid hormone (T3/T4) levels fall, reduced negative feedback prompts increased TRH and TSH secretion to stimulate the thyroid gland.
Which regulatory mechanism is least likely to apply to the secretion of prolactin from the anterior pituitary under physiological conditions?
- A Inhibitory regulation by dopamine from the hypothalamus
- B Stimulation by thyrotropin-releasing hormone (TRH)
- C Positive feedback from elevated prolactin levels
- D Suppression by high estrogen levels
Correct answer: Positive feedback from elevated prolactin levels
Prolactin release is primarily under inhibitory control by hypothalamic dopamine, with additional modulation by TRH and estrogen; it is not classically regulated by positive feedback from its own levels.
Which of the following endocrine regulation scenarios illustrates a ‘short-loop’ negative feedback mechanism?
- A Thyroid hormone inhibiting hypothalamic TRH release
- B Cortisol inhibiting both CRH and ACTH release
- C Pituitary hormone inhibiting hypothalamic releasing hormone secretion
- D Pancreatic insulin inhibiting glucagon secretion
Correct answer: Pituitary hormone inhibiting hypothalamic releasing hormone secretion
Short-loop negative feedback refers to a pituitary hormone acting back on the hypothalamus to inhibit secretion of its releasing hormone — matching 'pituitary hormone inhibiting hypothalamic releasing hormone secretion.' Thyroid hormone or cortisol inhibiting the hypothalamus/pituitary are long-loop feedback, and insulin inhibiting glucagon is local paracrine regulation within the pancreas, not a short-loop axis mechanism.
Which of the following glands is considered a ‘secondary’ endocrine gland (i.e., not primarily endocrine) but still contributes to endocrine regulation?
- A Adrenal gland
- B Thyroid gland
- C Pancreas
- D Pituitary gland
Correct answer: Pancreas
The pancreas is often considered a secondary endocrine gland — its main function is digestive (exocrine), but its islets secrete hormones (insulin, glucagon) contributing to endocrine regulation.
Which of the following best describes how sex steroids regulate the HPG axis in adults under normal conditions?
- A Positive feedback of testosterone on GnRH release in males
- B Negative feedback of sex steroids on hypothalamus and pituitary
- C Stimulation of GnRH release by estrogen in both sexes
- D Inhibition of GnRH by gonadal peptides exclusively
Correct answer: Negative feedback of sex steroids on hypothalamus and pituitary
Gonadal sex steroids (e.g., testosterone, estrogen) exert negative feedback on the hypothalamus and anterior pituitary to suppress GnRH and LH/FSH secretion, thereby regulating the HPG axis.
Which physiologic effect is most directly mediated by glucocorticoids like cortisol during prolonged stress?
- A Increased insulin secretion causing hypoglycemia
- B Enhanced immune response
- C Increased gluconeogenesis and blood glucose
- D Increased immune cell proliferation
Correct answer: Increased gluconeogenesis and blood glucose
Glucocorticoids such as cortisol promote gluconeogenesis, raising blood glucose — a key component of the metabolic adaptation to prolonged stress.
Which of the following best describes the role of the median eminence in endocrine regulation?
- A It stores and releases cortisol into the blood
- B Where hypothalamic releasing hormones enter the portal blood
- C It directly secretes thyroid hormone into circulation
- D It converts thyroxine (T4) to active T3
Correct answer: Where hypothalamic releasing hormones enter the portal blood
The median eminence is a hypothalamic region where releasing hormones are secreted into the hypophyseal-portal blood vessels and transported to the anterior pituitary to regulate pituitary hormone secretion.
Which of the following describes an endocrine control mechanism where a hormone from a target gland rapidly suppresses its upstream regulators (within minutes)?
- A Slow (genomic) negative feedback
- B Fast (non-genomic) negative feedback
- C Positive feedback
- D Long-loop positive feedback
Correct answer: Fast (non-genomic) negative feedback
Fast (non-genomic) negative feedback — such as rapid feedback inhibition of the HPA axis by cortisol — can suppress upstream hormone release within minutes, independent of gene transcription.
Which of the following is NOT a typical mode of stimulus for hormone secretion in endocrine glands?
- A Humoral (blood-borne) stimuli
- B Neural (nervous system) stimuli
- C Hormonal (tropic) stimuli
- D Mechanical stretch stimuli
Correct answer: Mechanical stretch stimuli
Typical modes of endocrine gland stimulation include humoral (blood-based), neural (nerve signals), or hormonal (from other glands). Mechanical stretch is not a standard mode of endocrine hormone release.
Which gland pair is correctly matched with its primary endocrine output and a major physiological function?
- A Pancreas → cortisol → stress adaptation
- B Adrenal cortex → thyroid hormones → metabolic rate
- C Thyroid gland → T3/T4 → basal metabolic rate regulation
- D Pituitary posterior lobe → insulin → blood glucose control
Correct answer: Thyroid gland → T3/T4 → basal metabolic rate regulation
The thyroid gland secretes T3 and T4, which are key regulators of basal metabolic rate; this is a central endocrine function.
Which situation would likely lead to increased (GH) secretion from the anterior pituitary?
- A High somatostatin release from hypothalamus
- B Sustained high blood glucose levels
- C Ghrelin release during fasting
- D High circulating IGF-1 concentrations
Correct answer: Ghrelin release during fasting
Ghrelin, released during fasting, stimulates growth hormone (GH) secretion. In contrast, high somatostatin, sustained high blood glucose, and high circulating IGF-1 all inhibit GH release through inhibitory hormones or negative feedback.