MLT GlobeChemistry: Endocrinology – page 4
123 Chemistry MCQs on Endocrinology with answers and explanations.
Which of these hormones is a steroid?
Aldosterone is a steroid made from cholesterol in the adrenal cortex. Insulin and TSH are peptide/protein hormones and epinephrine is an amino acid (catecholamine) derivative.
In the ovarian follicle, FSH mainly stimulates granulosa cells to make which hormone?
FSH induces aromatase, which converts theca-derived androgens to estradiol. After ovulation, LH mainly drives progesterone from the corpus luteum.
A 35-year-old woman has had amenorrhoea for 8 months, with high FSH and LH and low estradiol. What is the most likely cause?
Failing ovaries give no negative feedback, so gonadotrophins rise (hypergonadotropic hypogonadism). Pituitary, hypothalamic and prolactin causes give low or normal FSH/LH.
A man with low serum testosterone has high LH and FSH. Where is the lesion?
Low testosterone with high gonadotrophins means the testes are not responding. Pituitary or hypothalamic disease gives low or inappropriately normal LH/FSH.
A patient passes large volumes of dilute urine, with urine osmolality rising well after desmopressin. What is the diagnosis?
A good response to desmopressin shows the kidney works but ADH is lacking. In nephrogenic DI the kidney does not respond to ADH.
A patient has episodes of palpitations, headache and sweating with high blood pressure. Which test best screens for catecholamine excess?
Suspected phaeochromocytoma is screened with metanephrines, the O-methylated metabolites of adrenaline and noradrenaline. They are produced continuously and are more sensitive than catecholamines.
An adult has coarse facial features, enlarged hands and a deepening voice. Which test result confirms the likely diagnosis?
Acromegaly comes from GH excess, which thickens soft tissues including the larynx. It is confirmed by high IGF-1 and GH that does not suppress after oral glucose.
In second-trimester maternal serum screening, which marker is typically about 25% lower with a Down syndrome pregnancy?
The quad-screen pattern for trisomy 21 is low AFP, low uE3, high hCG and high inhibin A.
After a long-standing urinary tract obstruction is relieved, a patient passes large volumes of dilute urine that does not respond to desmopressin. What is the likely cause?
Chronic obstruction damages collecting ducts and reduces aquaporin-2, so ADH has no effect. Sheehan syndrome and vasopressin gene mutations cause central DI.
A patient on long-term steroids stops them suddenly and presents with hypotension, vomiting and hypoglycaemia. Which description fits this emergency?
Stopping steroids after HPA-axis suppression leaves too little cortisol, causing shock and hypoglycaemia. This is an adrenal (Addisonian) crisis, treated with IV hydrocortisone.
Which statement about multiple endocrine neoplasia (MEN) syndromes is correct?
MEN1 (MEN1 gene) and MEN2 (RET) are autosomal dominant and affect several endocrine glands. The type of tumour and degree of hormone rise vary.
To confirm that ovulation has occurred in a regular 28-day cycle, which test is best, and when is it taken?
A mid-luteal progesterone above about 30 nmol/L shows a corpus luteum and so confirms ovulation. Day 2–3 FSH assesses ovarian reserve.
What happens to LH and FSH in a normal ovulatory cycle?
Rising estradiol triggers positive feedback and a mid-cycle LH surge, with a smaller FSH peak. The LH surge begins about 24–36 hours before ovulation and peaks about 10–12 hours before it; urine LH kits detect this surge.
A young woman with a very low BMI and amenorrhoea has blood tests. Which result is expected?
In anorexia nervosa, energy deficit suppresses hypothalamic GnRH, causing hypogonadotropic hypogonadism. Very high FSH would suggest ovarian failure.
A woman with regular 35-day cycles is being checked for ovulation. When should serum progesterone be measured?
Progesterone peaks about 7 days after ovulation. In a 35-day cycle ovulation is around day 21, so the sample is taken around day 28.
Which change most directly stimulates the adrenal zona glomerulosa to secrete aldosterone?
Angiotensin II (from renin release) and hyperkalaemia are the main drivers of aldosterone. ACTH has only a minor, short-term effect.
In suspected acromegaly, which statement about laboratory diagnosis is correct?
Because GH is pulsatile, random values overlap with normal. Raised IGF-1 plus failure of GH to suppress after 75 g glucose confirms the diagnosis.
Which biochemical finding most consistently goes with primary hyperparathyroidism?
PTH reduces proximal tubular phosphate reabsorption, so serum phosphate falls while calcium rises. Hyperchloraemic acidosis, not alkalosis, may occur.
How does measuring PTH help when a patient has hypocalcaemia?
Low PTH with low calcium means hypoparathyroidism. High PTH means an appropriate response, as in vitamin D deficiency, CKD or PTH resistance (pseudohypoparathyroidism).
A patient with squamous cell lung cancer has high calcium and suppressed PTH. Which mediator is most likely?
Humoral hypercalcaemia of malignancy is mostly caused by PTHrP, which activates the PTH receptor but is not detected by PTH assays. Ectopic PTH is very rare.