Instructions: Select the single best answer. Explanations appear immediately after each response. Your scores populate the Score Report tab in real time.
Question 1 of 5 — LO 1 · Portal System
A researcher injects a rapidly-cleared dye into the median eminence of a rat brain and observes the pattern of dye distribution over 10 seconds. The dye first appears in small capillaries at the base of the hypothalamus, then enters a set of veins running down the infundibulum, and finally diffuses into a second capillary bed. In which structure does the dye ultimately appear in this second capillary bed?
ANeurohypophysis (posterior pituitary)
BAdenohypophysis (anterior pituitary)
CPineal gland
DSupraoptic nucleus
ECavernous sinus
B — Adenohypophysis. The classic hypophyseal portal system: first capillary plexus in the median eminence (a circumventricular organ — no BBB) → portal veins in the infundibulum → second capillary plexus in the anterior pituitary. This two-plexus route delivers hypothalamic releasing/inhibiting hormones in HIGH local concentration to anterior pituitary cells without diluting them systemically. Posterior pituitary (A) uses a DIFFERENT system — direct axonal projections + regular arterial blood supply.
Question 2 of 5 — LO 2 · Hypothalamic Nuclei
A 32-year-old woman with schizophrenia has been on risperidone (D2 antagonist) for 3 years. She develops amenorrhea, galactorrhea, and fatigue. Her serum prolactin is 180 ng/mL. Dysregulation of which hypothalamic nucleus best explains the rise in prolactin caused by this medication?
ASupraoptic nucleus
BParaventricular nucleus
CArcuate nucleus
DVentromedial nucleus
EMedial preoptic nucleus
C — Arcuate nucleus. The arcuate nucleus is the source of dopamine (PIH / prolactin-inhibiting hormone), which TONICALLY INHIBITS prolactin release from anterior pituitary lactotropes. Risperidone and other D2 antagonists block the dopamine receptor on lactotropes → loss of tonic inhibition → ↑PRL. SON/PVN (A, B) make ADH and oxytocin. VMN (D) makes GHRH. Medial preoptic (E) makes GnRH. Tests LO 2 (nuclei ↔ hormones) applied to drug-induced hyperprolactinemia.
Question 3 of 5 — LO 3 · Histology
A 58-year-old woman undergoes transsphenoidal resection of a pituitary adenoma. Histology shows a monomorphic population of tumor cells with eosinophilic cytoplasm on H&E. Immunohistochemistry is positive for a single peptide hormone. Preoperative serum studies revealed markedly elevated IGF-1 and failure of GH to suppress with oral glucose. From which cell type did this tumor most likely arise?
ASomatotrope (acidophil)
BCorticotrope (basophil)
CThyrotrope (basophil)
DGonadotrope (basophil)
EChromophobe
A — Somatotrope. Acidophilic (eosinophilic) anterior pituitary cells are either somatotropes (GH) or lactotropes (PRL). Elevated IGF-1 + failure of GH to suppress with OGTT = acromegaly → somatotrope adenoma. Basophils (B–D) stain with hematoxylin and produce the other four hormones ("B-FLAT": basophils = FSH, LH, ACTH, TSH). Chromophobes (E) are non-secretory supporting cells. This question explicitly tests LO 3 histology linked to the clinical endpoint.
Question 4 of 5 — LO 3 · Embryology
A 7-year-old boy with progressive headache, vomiting, and visual field defects is found on MRI to have a suprasellar mass with prominent calcifications. Surgical biopsy reveals a cystic tumor with squamous epithelium and "machine-oil"–like fluid rich in cholesterol crystals. The epithelial component of this tumor arose from a remnant of which embryologic structure?
ARathke's pouch (oral ectoderm)
BDiencephalon (neuroectoderm)
CNeural crest cells
DBranchial (pharyngeal) pouch
ENotochord
A — Rathke's pouch. Craniopharyngioma — the classic tumor of childhood arising from Rathke's pouch remnants (oral ectoderm that forms the adenohypophysis). The calcifications + "machine-oil" cyst contents + suprasellar location + bitemporal hemianopia pattern is pathognomonic. The neurohypophysis, in contrast, comes from diencephalic neuroectoderm (B). Reinforces LO 3 embryologic origin of the two pituitary lobes.
Question 5 of 5 — LO 1/2 · Circumventricular Organs & Nonapeptides
A researcher studies four brain regions known to lack a blood-brain barrier (circumventricular organs). Region 1 — the median eminence — allows hypothalamic releasing hormones to enter portal blood. Region 2 — the neurohypophysis — is the release site for ADH and oxytocin, which are synthesized in SON/PVN and concentrate in eosinophilic axon-terminal swellings. Region 3 — the OVLT — hosts specialized osmoreceptor neurons that detect plasma hyperosmolarity and project back to the SON/PVN to trigger ADH release. Region 4 — the pineal gland — releases melatonin into blood.
The eosinophilic axon-terminal swellings in region 2 are known as:
ANissl bodies
BPsammoma bodies
CHerring bodies
DBirbeck granules
ERussell bodies
C — Herring bodies. These are the swollen axon terminals of SON/PVN neurons where ADH and oxytocin (the nonapeptides) are stored bound to neurophysins before release into fenestrated capillaries of the posterior pituitary.
The broader framework: these four regions — median eminence, neurohypophysis, OVLT, pineal — are circumventricular organs (CVOs). They sit close to the ventricles and lack a tight BBB, which uniquely allows blood-borne molecules (hormones, drugs like desmopressin) to interact with CNS tissue directly. The area postrema (chemoreceptor trigger zone) and subfornical organ are two more CVOs with clinical importance. Damage to the OVLT specifically produces adipsic DI — loss of osmoreceptor-driven ADH AND loss of thirst.
Instructions: Select the single best answer. Questions emphasize specific hypothalamic-pituitary axis regulation and feedback-loop logic.
Question 1 of 5 — LO 4 · Prolactin Regulation
A 45-year-old man is admitted after a motor vehicle collision with basilar skull fracture and pituitary stalk disruption confirmed on MRI. On hospital day 3, his serum labs show: cortisol 2.1 µg/dL (low), free T4 0.4 ng/dL (low), testosterone 62 ng/dL (low), and — unexpectedly — prolactin 78 ng/mL (elevated). Which of the following best explains the selective rise in prolactin despite global anterior pituitary insufficiency?
AEctopic prolactin secretion from injured brain tissue
BPreexisting undiagnosed prolactinoma
CLoss of dopamine delivery from hypothalamus to lactotropes due to stalk injury
DStress-induced elevation from surgical trauma
ECross-reactivity of PRL assay with GH
C. Prolactin is the ONLY anterior pituitary hormone under TONIC INHIBITION (by arcuate-nucleus dopamine reaching lactotropes via the portal system). All other AP hormones require POSITIVE releasing factors. Stalk injury abolishes BOTH: releasing factors can't reach their targets (→ ↓TSH, ↓ACTH, ↓LH/FSH, ↓GH), and dopamine can't reach lactotropes (→ ↑PRL). This classic "stalk effect" pattern is pathognomonic and directly tests LO 4.
Question 2 of 5 — LO 4 · GH Axis
A 36-year-old man has enlarged hands, coarse facial features, new hypertension, and sleep apnea. Random serum GH is 4 ng/mL (normal <1 in healthy adults). An oral glucose tolerance test is performed: at 2 hours, GH is 5.2 ng/mL (normal response: suppression below 1 ng/mL). Serum IGF-1 is 3× the upper limit of normal. Why is the OGTT a better CONFIRMATORY test than random GH in this patient?
AGH is bound to IGFBPs and cannot be measured directly
BGH is secreted pulsatilely, so a random value is unreliable, but failure to suppress with glucose demonstrates autonomous (non-physiologic) secretion
CGlucose directly assays the somatotrope tumor
DIGF-1 does not rise until GH has been elevated for 6 months
EGlucose stimulates GHRH in normal subjects
B. Normal GH secretion is highly PULSATILE (driven by GHRH pulses + ultra-short autoregulation, nocturnal peaks, stress/exercise bursts). A single random measurement can be high in a normal person or low in an acromegalic at a trough. Glucose normally suppresses GH via long-loop metabolic feedback (insulin/IGF-1-mediated). In acromegaly, the tumor ignores this feedback → GH remains high after oral glucose. Failure to suppress is the diagnostic gold standard. Tests LO 5 feedback/pulsatility principle.
Question 3 of 5 — LO 5 · Long vs. Short Loop
A researcher studies negative feedback in the cortisol axis. In experiment A, infusion of dexamethasone (a synthetic glucocorticoid) into a rat's jugular vein causes a marked decrease in both CRH and ACTH. In experiment B, microinjection of ACTH directly into the rat's hypothalamus causes a decrease in CRH but has no effect on anterior pituitary ACTH. In experiment C, microinjection of CRH into the median eminence causes a transient decrease in CRH release from adjacent hypothalamic nuclei. Which feedback loops are being demonstrated in experiments A, B, and C, respectively?
AA = long loop; B = short loop; C = ultra-short loop
BA = short loop; B = long loop; C = positive feedback
CA = ultra-short; B = long; C = short
DA = long; B = ultra-short; C = short
EAll three are examples of positive feedback
A. Long loop = target-organ (or target-mimicking) hormone → suppresses hypothalamus AND pituitary (dex = cortisol-mimicking → ↓CRH + ↓ACTH). Short loop = pituitary hormone → suppresses hypothalamus (ACTH → ↓CRH). Ultra-short loop = hypothalamic hormone → suppresses its OWN release via axon collaterals (CRH → ↓CRH), generating pulsatility. This is a direct conceptual test of LO 5 feedback hierarchy.
Question 4 of 5 — LO 5 · Positive Feedback / LH Surge
A 28-year-old woman has her pituitary and ovarian hormones measured daily through one menstrual cycle. On day 11, estradiol is 320 pg/mL (high, end of follicular phase); on day 12, LH surges from 20 → 78 mIU/mL; ovulation follows on day 13. In the luteal phase, progesterone rises markedly and estradiol remains high, but LH remains suppressed. Which feedback mechanism best accounts for the LH surge on day 12?
ARising progesterone exerts positive feedback on GnRH and LH
BHigh sustained estradiol switches from negative to positive feedback on GnRH → LH
CUltra-short-loop feedback of GnRH causes auto-excitation
DInhibin B switches from inhibition to stimulation of FSH
EFSH directly stimulates LH receptors on gonadotropes
B. One of two classic positive-feedback scenarios in endocrine physiology. High, sustained estradiol (above ~200 pg/mL for >48 h) flips the GnRH/LH response from suppression to activation → massive LH surge → ovulation. Once ovulation occurs, the corpus luteum produces progesterone, which RESTORES negative feedback — so even though estradiol stays high, LH is suppressed in the luteal phase. Progesterone NEVER exerts positive feedback in this system. The other positive-feedback example is oxytocin/labor.
Question 5 of 5 — LO 4/5 · Pulsatility Principle
A 28-year-old man with idiopathic hypogonadotropic hypogonadism (low LH, FSH, testosterone; small testes; infertility) is being treated for fertility. Therapy option 1: daily injection of long-acting GnRH agonist. Therapy option 2: subcutaneous infusion pump delivering GnRH in 75-ng pulses every 90 minutes. Over 2 weeks, option 1 causes LH and FSH to fall to undetectable levels, while option 2 restores them toward normal. Which principle best explains this contrast?
ALong-acting GnRH agonists have weaker affinity for the GnRH receptor than endogenous GnRH
BContinuous GnRH stimulation causes down-regulation of pituitary GnRH receptors; pulsatile delivery preserves receptor sensitivity
CPulsatile delivery results in higher cumulative GnRH exposure
DContinuous GnRH is metabolized differently in the liver
EOnly pulsatile GnRH reaches the pituitary through the portal system
B. The LO 5 pulsatility principle in pure form. Continuous GnRH → receptor down-regulation on pituitary gonadotropes (same receptor mass, but internalized / desensitized) → LH/FSH fall. This is exactly why leuprolide given CONTINUOUSLY is used as "chemical castration" for prostate cancer and endometriosis. Pulsatile GnRH mimics the physiologic every-60-to-90-minute hypothalamic rhythm → LH/FSH respond normally → fertility can be restored (e.g., in Kallmann syndrome, hypothalamic amenorrhea). The same principle applies broadly — many hormones require pulsatility to avoid receptor desensitization.
Instructions: Apply the primary/secondary/tertiary framework and exogenous-hormone logic to classic clinical scenarios.
Question 1 of 5 — Sheehan Syndrome
A 31-year-old woman delivered a healthy term infant 6 weeks ago after an obstetric course complicated by severe postpartum hemorrhage (blood loss ~2,800 mL) requiring 5 units of PRBC. She reports persistent fatigue, inability to breastfeed, no return of menses, cold intolerance, and orthostatic lightheadedness. Labs: TSH 0.5 (low-normal), free T4 0.5 ng/dL (low), prolactin <1 ng/mL (very low), 8 AM cortisol 2.4 µg/dL (low), ACTH 8 pg/mL (low), LH <0.5 IU/L, FSH 1.1 IU/L. Urine osmolality and serum Na⁺ are normal. A plasma metanephrine measurement is normal and she mounts a normal tachycardic response to orthostasis. Which of the following best explains ALL of her findings, including the preserved posterior-pituitary and adrenal-medullary function?
AIschemic necrosis of the pregnancy-hypertrophied anterior pituitary; posterior pituitary spared (different arterial supply); adrenal medulla spared (controlled by direct sympathetic innervation, not ACTH)
BLymphocytic hypophysitis — autoimmune destruction of all pituitary cells
CPrimary hypothyroidism from postpartum thyroiditis with secondary pituitary suppression
DEmpty sella syndrome incidentally discovered postpartum
ECentral diabetes insipidus from pituitary stalk injury
A — Sheehan syndrome. Pregnancy doubles lactotrope mass, making the anterior pituitary dependent on increased portal flow. Major postpartum hemorrhage → hypotension → ischemic necrosis of the anterior lobe. LOW prolactin → failure to lactate (classically the first sign). LOW LH/FSH → amenorrhea. LOW TSH → secondary hypothyroidism. LOW ACTH → adrenal cortex insufficiency. Posterior pituitary SPARED — different arterial supply explains preserved ADH (normal Na⁺ + osm). Adrenal MEDULLA SPARED because it is controlled by DIRECT sympathetic innervation (not ACTH) — a separate hypothalamic output pathway. This is why the patient's tachycardic response and plasma metanephrines remain intact despite global pituitary insufficiency. LO 1/4/6 integration.
Question 2 of 5 — Exogenous Steroid Withdrawal
A 55-year-old man with polymyalgia rheumatica has been on prednisone 20 mg daily for 14 months. He feels well-controlled and stops taking the medication abruptly. Two days later, he presents to the ED with nausea, severe fatigue, diffuse abdominal pain, and hypotension (BP 82/50). Labs: Na⁺ 129, K⁺ 3.9 (normal), glucose 58, cortisol <1 µg/dL, ACTH 8 pg/mL (low). Aldosterone and renin are normal. Which of the following best describes the pathophysiology of his condition?
AAutoimmune destruction of the adrenal cortex (Addison's)
BChronic long-loop suppression of CRH and ACTH → adrenal atrophy; abrupt withdrawal of exogenous glucocorticoid left him with neither endogenous cortisol nor adrenal capacity to respond
CPituitary apoplexy
DBilateral adrenal hemorrhage (Waterhouse-Friderichsen syndrome)
EIsolated mineralocorticoid deficiency
B. Chronic exogenous glucocorticoid → long-loop feedback suppresses CRH AND ACTH → adrenal zona fasciculata atrophies over weeks-months. When the drug is stopped abruptly, endogenous cortisol production cannot restart quickly. Notice aldosterone and renin are normal — the zona glomerulosa is NOT ACTH-dependent and remains functional (which is why hyperkalemia from mineralocorticoid deficiency is absent here, unlike primary Addison's). Classic LO 6 "exogenous hormone" case. Always taper chronic steroids; stress-dose during illness.
Question 3 of 5 — Secondary vs. Tertiary Hypothyroidism
A 48-year-old man is diagnosed with hypothyroidism based on labs: free T4 0.4 ng/dL (LOW), TSH 1.0 mIU/L (inappropriately low-normal). Endocrinology orders a TRH stimulation test: after IV TRH administration, TSH rises briskly from 1.0 to 18 mIU/L at 30 minutes and returns to baseline by 2 hours. This response pattern is most consistent with which of the following?
APrimary hypothyroidism (thyroid gland failure)
BSecondary hypothyroidism (pituitary TSH failure)
CTertiary hypothyroidism (hypothalamic TRH failure)
DEuthyroid sick syndrome from chronic illness
EThyroid hormone resistance (TRβ mutation)
C — Tertiary (hypothalamic). If the pituitary is intact but wasn't receiving TRH, it will RESPOND briskly when exogenous TRH is provided → TSH rises normally or even exaggeratedly. If the problem were pituitary (B), exogenous TRH would not elicit much TSH rise because the gland itself is damaged. Primary (A) has HIGH baseline TSH. Thyroid resistance (E) has HIGH T4 + HIGH TSH. This test is a pure application of LO 6 — distinguishing hypothalamic from pituitary failure by adding the missing releasing hormone.
Question 4 of 5 — Ectopic ACTH vs. Pituitary Cushing
A 70-year-old man with a 60-pack-year smoking history presents with 2 months of proximal muscle weakness, new hypertension (BP 190/110), edema, and severe hypokalemia (K⁺ 2.5). He also has notable hyperpigmentation of skin creases and gums. Labs: 24-hr urine free cortisol 8× normal; ACTH 380 pg/mL (very high). Low-dose dexamethasone suppression test fails to suppress cortisol. High-dose dexamethasone suppression also fails (no change in cortisol). CT chest reveals a 3-cm perihilar mass. What is the most likely diagnosis?
ACushing disease (pituitary ACTH-secreting adenoma)
BEctopic ACTH secretion from small-cell lung carcinoma
CAdrenal cortisol-secreting adenoma
DExogenous corticosteroid use
EPseudo-Cushing from alcohol use
B — Ectopic ACTH. Key: BOTH low- AND high-dose dex fail to suppress → tumor is feedback-INDEPENDENT. Very high ACTH + hyperpigmentation (POMC cleavage produces MSH along with ACTH) + severe hypokalemic alkalosis (excess cortisol overwhelms 11β-HSD2 and acts at mineralocorticoid receptors) + lung mass in a smoker = small-cell lung carcinoma. Pituitary Cushing disease (A) SUPPRESSES at high dose. Adrenal (C) + exogenous (D) have LOW ACTH. Directly tests LO 5/6 feedback logic in a classic clinical integration.
Question 5 of 5 — Kallmann Syndrome
A 17-year-old boy is evaluated for delayed puberty. He has no axillary or pubic hair, small testes (3 mL volume), and has never detected olfactory cues in a standardized smell test. Labs: LH 0.8 IU/L (low), FSH 1.5 IU/L (low), testosterone 28 ng/dL (very low), prolactin normal. MRI shows absent olfactory bulbs but otherwise normal pituitary and hypothalamus. Genetic testing reveals a mutation in ANOS1 (KAL1). Which of the following best describes the underlying problem?
APrimary testicular failure (hypergonadotropic hypogonadism)
BKlinefelter syndrome (47,XXY)
CFailure of GnRH neurons to migrate from the olfactory placode to the hypothalamus
DAndrogen receptor mutation (complete androgen insensitivity)
EPituitary macroadenoma with gonadotrope compression
C — Kallmann syndrome. GnRH neurons arise from the olfactory placode and migrate into the hypothalamus alongside olfactory neurons. KAL1 (ANOS1) mutations disrupt this migration → absent olfactory bulbs (anosmia) + absent hypothalamic GnRH → hypogonadotropic hypogonadism (LOW LH/FSH → LOW T). Klinefelter (B) = HIGH LH/FSH (hypergonadotropic — primary testicular failure). AIS (D) has normal-to-high T. Classic tertiary/central deficiency via developmental anatomy — a beautiful LO 2/4/6 integration question.
Source review. Every item below was pulled from your 3rd Party Biochem + Physio folders and hand-mapped to END02 Hypothalamic-Pituitary Relationships (Part 1) LOs — anatomical connections, hypothalamic nuclei and their hormones, pituitary organization, pituitary hormones and their hypothalamic regulation, feedback loops, and predicting axis-level changes. Grouped by LO to complement — not duplicate — the in-house exam Blocks 1-3 above.
Legend:
BRS Biochem
BRS Physio
Waite & Sheakley
Group A · Anatomy & Cell-of-Origin (LOs 1, 3)
Ext Q1 — LO 3 · Neuroectodermal Origin — Waite & Sheakley Q7
A 75-year-old woman complains of bilateral temporal hemianopsia, and imaging of the head reveals a suprasellar granular cell tumor. The tumor is excised, and immunohistochemical studies using biomarkers are performed in order to determine the tumor cell origin. A positive reaction for which of the following hormones would indicate that the tumor is of neuroectodermal origin?
AAdrenocorticotropic hormone (ACTH)
Bβ-endorphin
CLuteinizing hormone (LH)
DOxytocin
EThyroid-stimulating hormone (TSH)
D — Oxytocin. The posterior pituitary (neurohypophysis) is an extension of the hypothalamus — it develops from neuroectoderm and stores oxytocin and ADH (synthesized in the paraventricular and supraoptic nuclei). The anterior pituitary (adenohypophysis) is derived from oral ectoderm (Rathke pouch) and makes ACTH (with β-endorphin from POMC cleavage), LH, FSH, TSH, GH, and PRL. LO 3 at the embryology-meets-histology level: oxytocin positivity = neural lobe, all the others = oral-ectoderm-derived anterior lobe.
Ext Q2 — LO 1 · Hypophyseal Portal Disruption — Waite & Sheakley Q8
A male soldier experienced severe head trauma that resulted in permanent interruption of his hypothalamohypophyseal portal vessels. Which of the following would be expected to develop?
AAcromegaly
BExcessive aggressiveness (↑ testosterone)
CHyperpigmentation
DHyperprolactinemia
EHyperthyroidism
D — Hyperprolactinemia. The hypothalamic-hypophyseal portal system delivers ALL hypothalamic releasing/inhibiting hormones to the anterior pituitary in high local concentration. Prolactin is uniquely under tonic inhibition by hypothalamic dopamine (PIF). Cut the portal system → dopamine can't reach the lactotrophs → disinhibition → PRL ↑ (the "stalk effect"). Every OTHER anterior pituitary hormone is tonically STIMULATED, so portal loss DECREASES them: GHRH loss ↓ GH (no acromegaly, A), GnRH loss ↓ LH/FSH (↓ testosterone, not ↑, so B is wrong), CRH loss ↓ ACTH/POMC (no hyperpigmentation, C), TRH loss ↓ TSH (no hyperthyroidism, E). This is the single most test-worthy LO 1 mechanism.
Group B · Pituitary Hormones & Hypothalamic Regulation (LOs 2, 4)
Ext Q3 — LO 4 · Dopamine as PIF — BRS Biochem Q13
A 32-year-old female presents with 3 months of irregular menstrual periods and a milky discharge from both breasts. Under the microscope, the discharge has many fat globules, but no red blood cells. She is on no medications, has had a bilateral tubal ligation, and her pregnancy test is negative. Which ONE of the following would inhibit the release of the hormone that is being overproduced in this patient?
AGnRH
BDopamine
CTRH
DSomatostatin
EEstradiol
B — Dopamine. This is a prolactinoma of the anterior pituitary. Hypothalamic dopamine (PIF) tonically inhibits lactotroph PRL release — classic test detail for LO 4. Clinical payoff: dopamine AGONISTS like bromocriptine and cabergoline shrink prolactinomas. GnRH (A) inhibits LH/FSH, not PRL. TRH (C) actually STIMULATES PRL release (a key reason primary hypothyroidism causes hyperprolactinemia). Somatostatin (D) inhibits GH. Estradiol (E) STIMULATES PRL synthesis.
Ext Q4 — LO 4 · Post-Traumatic Galactorrhea — Waite & Sheakley Q11
A 30-year-old woman is diagnosed with galactorrhea from both breasts. She is not pregnant and has never been pregnant. The nipple discharge started two weeks ago, after she was in a car accident. She had a concussion and is still having headaches. The galactorrhea is most likely a result of which substance not reaching the pituitary gland?
ADopamine
BGonadotropin-releasing hormone (GnRH)
CGrowth hormone–releasing hormone (GHRH)
DOxytocin
EThyrotropin-releasing hormone (TRH)
A — Dopamine. Same physiology as Ext Q2 applied clinically. Traumatic brain injury can interrupt either the long portal veins or the periventricular dopaminergic axons running down the pituitary stalk — in either case lactotrophs are disinhibited → hyperprolactinemia → galactorrhea. All the other choices (GnRH, GHRH, oxytocin, TRH) actually SUPPORT or stimulate prolactin release — missing them would REDUCE prolactin. Think of dopamine as the one "braking" signal in the entire hypothalamic-pituitary system.
Ext Q5 — LO 4 · GnRH Deficiency — BRS Biochem Q34
An individual has a mutation such that GnRH release is greatly reduced. This mutation would have its greatest effects on the release of which one of the following?
AGrowth hormone (GH)
BT3 and T4
CProlactin (PRL)
DInsulin-like growth factor (IGF)
ELH and FSH
E — LH and FSH. One-to-one mapping of hypothalamic → anterior pituitary hormones (LO 4): GnRH → LH + FSH, GHRH → GH (and GH → IGF-1 from liver), TRH → TSH + PRL, CRH → ACTH, and dopamine → ↓PRL. GnRH deficiency underlies Kallmann syndrome (when associated with anosmia). Downstream: ↓LH/FSH → hypogonadotropic hypogonadism → ↓ sex steroids, infertility.
Ext Q6 — LO 4 · ADH Analog for Central DI — Waite & Sheakley Q9
A 17-year-old boy previously sustained a severe fracture at the base of his skull while skateboarding. He presents with increased thirst and polyuria. His urine is pale in color with a low specific gravity. He has a blood pressure of 98/50 mm Hg, has tachycardia, and is very weak. An analogue of which of the following hormones is most likely prescribed for treatment?
AAdrenocorticotropic hormone (ACTH)
BAldosterone
CAndrostenedione
DAngiotensin II
EAntidiuretic hormone (ADH / vasopressin)
E — ADH (desmopressin). Classic central diabetes insipidus after stalk / skull-base injury: polyuria + polydipsia + pale, dilute urine + hypotension + tachycardia from volume depletion. ADH is synthesized in hypothalamic supraoptic + paraventricular nuclei (LO 2) and released from posterior pituitary; when axonal transport is severed, ADH-deficient polyuria results. Desmopressin (DDAVP) is a selective V2 agonist that restores water reabsorption without V1 vasoconstrictor effects. Note: nephrogenic DI would NOT respond to DDAVP.
Group C · Feedback Loops (LO 5)
Ext Q7 — LO 5 · Iodine Deficiency Feedback — BRS Biochem Q35
A teenager in Australia has developed a goiter, due to a dietary deficiency. Which row best describes the expected changes in this dietary deficiency?
Salt balance TSH TRH Heat
altered? secretion secretion production
A. No Increased Increased Increased
B. Yes Increased Decreased Increased
C. No Increased Increased Decreased
D. Yes Decreased Decreased Decreased
E. No Decreased Increased Decreased
F. Yes Decreased Decreased Increased
ARow A
BRow B
CRow C
DRow D
ERow E
FRow F
C. Dietary iodine deficiency → thyroid can't make enough T3/T4 → LOSS of negative feedback on hypothalamus + pituitary → TRH ↑ and TSH ↑. Chronic TSH stimulation hyperplastes the gland → goiter. Because T3/T4 are low, basal metabolic rate drops → heat production ↓ (not ↑). Iodine does NOT affect salt balance (aldosterone axis). This question tests LO 5 end-to-end: feedback origin (thyroid hormone) → feedback target (hypothalamus AND pituitary) → net effect on both upstream hormones.
Ext Q8 — LO 5 · TRH Stimulation Test Baseline — Waite & Sheakley Q28
As part of a TRH stimulating test, TRH is injected into a healthy adult at time zero and peripheral blood samples are taken at 0, 20, and 60 minutes to measure TSH. The baseline TSH at time zero is 2 mU/L. Which of the following best describes the expected 20-min and 60-min TSH levels?
A20 min: 2 mU/L · 60 min: 15 mU/L
B20 min: 2 mU/L · 60 min: 45 mU/L
C20 min: 15 mU/L · 60 min: 45 mU/L
D20 min: 15 mU/L · 60 min: 10 mU/L
E20 min: 15 mU/L · 60 min: 2 mU/L
D — 15 then 10 mU/L. Two kinetic principles from LO 5: (1) TRH stimulates pituitary TSH release quickly because TSH is preformed and stored → peak within 20 min. (2) Hypothalamic TRH has a short half-life (minutes), while pituitary TSH has a longer half-life (hours). So at 60 min the TRH stimulus is gone but TSH is still partially elevated as negative feedback from rising T3/T4 slowly brings it back down. Choice E (rapid full return to baseline) requires faster feedback than physiology allows.
Ext Q9 — LO 5 · TRH Stim in Primary Hypothyroidism — Waite & Sheakley Q29
In the TRH stimulation test described above, in which of the following conditions would TSH be expected to rise promptly 20 minutes after TRH administration?
APrimary hyperthyroidism
BPrimary hypothyroidism
CSecondary hypothyroidism
DSecondary hyperthyroidism
ETertiary hyperthyroidism
B — Primary hypothyroidism. LO 5 localization of axis lesions: Primary = gland, Secondary = pituitary, Tertiary = hypothalamus. In primary hypothyroidism the thyroid is broken but the pituitary is fine — and is already running with low T3/T4 feedback, so TSH baseline is HIGH and the gland responds even more briskly to exogenous TRH. Primary HYPERthyroidism (A) has TSH fully suppressed by excess T3/T4 → no response. Secondary disorders (C, D) can't respond because the pituitary itself is the lesion. Tertiary HYPERthyroidism (E) means hypothalamic TRH is already excessive — adding more does little — and "tertiary hyper" is barely a real clinical entity anyway.
Group D · Predict the Axis (LO 6)
Ext Q10 — LO 6 · Panhypopituitarism Prediction — BRS Biochem Q30
Following an automobile accident, a 14-year-old girl developed diabetes insipidus (excessive loss of water in the urine), amenorrhea (lack of menses), and cold intolerance, and her growth rate slowed markedly. Her symptoms best correspond to which one of the following?
ADamage to her kidneys and ovaries caused by the accident
BDamage to her pituitary gland
CSymptoms could be relieved by oral doses of anterior and posterior pituitary hormones
DLong-term estrogen + thyroxine + glucocorticoid tablets and restriction of water intake
EDamage to the pancreas caused by airbag deployment
B — Pituitary damage (panhypopituitarism). LO 6: iterate every axis and look for multi-system dysfunction. ↓ ADH → central DI. ↓ LH/FSH → amenorrhea. ↓ TSH → low T3/T4 → cold intolerance, decreased BMR. ↓ GH → growth arrest (in a 14-year-old with open growth plates this is profound). Only a pituitary lesion hits all four axes at once. C is wrong because pituitary hormones are PEPTIDES — orally they'd be digested. D is wrong because water intake must be INCREASED, not restricted, and estrogen alone won't restore normal menses without gonadotropin support either. E can't explain DI or cold intolerance.
Ext Q11 — LO 4/6 · Secondary Hypothyroidism & Stalk Hormone Cross-Talk — Waite & Sheakley Q31
A 45-year-old woman presents with a 6-month history of excessive tiredness, unexpected weight gain, constipation, galactorrhea, and amenorrhea. Laboratory values show elevated TSH and FSH. A pregnancy test is negative. She denies any head injuries, and brain MRI is normal. Which of the following serum levels of TRH and GnRH are expected?
ATRH normal · GnRH ↑
BTRH normal · GnRH ↓
CTRH ↓ · GnRH normal
DTRH ↓ · GnRH ↑
ETRH ↑ · GnRH ↓
FTRH ↑ · GnRH normal
E — TRH ↑ · GnRH ↓. Textbook LO 4/6 cross-talk. Hypothyroidism + galactorrhea + amenorrhea → primary hypothyroidism. Mechanism: low T3/T4 → TRH ↑ (feedback). TRH is a strong PRL releaser, so PRL also ↑ → galactorrhea. High PRL inhibits hypothalamic GnRH → LH/FSH fall → amenorrhea. Note the question's "elevated FSH" is a distractor / lab timing artifact — the MECHANISTIC logic still says GnRH suppressed. Choice D would require a hypothalamic lesion, which the normal MRI contradicts. Great composite of LO 4 (regulatory cross-talk) + LO 6 (iterate the axis).
Ext Q12 — LO 2/6 · Drug-Induced TRH Stim → ↓ Libido — Waite & Sheakley Q32
Clinical trials determined that a new drug had the undesirable effect of stimulating TRH receptors. Which of the following is the most likely side effect experienced by male patients who took the medication?
AConstipation
BDecreased libido
CHair loss
DPremature ejaculation
EPretibial myxedema
B — Decreased libido. LO 2 detail: pituitary lactotrophs express TRH receptors (not just thyrotrophs). Drug-induced TRH stimulation → hyperprolactinemia. LO 6 iteration: elevated PRL inhibits the hypothalamic-pituitary-gonadal axis (↓ GnRH pulses) → ↓ LH/FSH → ↓ testosterone → decreased libido / erectile dysfunction. Constipation (A), hair loss (C), and pretibial myxedema (E) are features of hypothyroidism and Graves respectively — but stimulating TRH actually mimics mild hyperthyroidism downstream. Premature ejaculation (D) is more associated with hypoprolactinemia.