A 23-year-old woman has had irregular periods since menarche, acne and excess facial hair; her BMI is 31 kg/m². Day 3 results: LH 16 IU/L and FSH 5 IU/L (both 3-10), total testosterone 82 ng/dL (15-70), prolactin and TSH normal, early-morning 17-hydroxyprogesterone 0.9 ng/mL (below 2). The most likely diagnosis is:

Androgen-secreting adrenal tumour

Non-classic congenital adrenal hyperplasia

A 40-year-old woman has weakness, weight loss and darkening of her skin creases. Basal plasma ACTH is high, and serum cortisol does not rise 30 or 60 minutes after 250 µg of tetracosactide. These results indicate:

Suppression by long-term prednisolone

Organ function tests and hormones

48 Kerala MSc MLT Entrance practice questions on Organ function tests and hormones, part of Biochemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
In the Van Slyke urea clearance test, 'standard clearance' (U√V/P) replaces 'maximum clearance' (UV/P) when the urine flow is:
1. ABelow 2 mL per minute
2. BAbove 10 mL per minute
3. CAbove 2 mL per minute
4. DBelow 0.5 mL per minute
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Answer: A · Below 2 mL per minute
Urea is partly reabsorbed, and the amount reabsorbed depends on urine flow. Above about 2 mL/min, the augmentation limit, clearance is maximal and independent of flow, so UV/P is used (normal about 75 mL/min). Below 2 mL/min clearance varies with the square root of flow, so the standard clearance U√V/P is used (normal about 54 mL/min). Urea clearance has now been replaced by creatinine clearance and eGFR.
- B: The cut-off between the two formulas is 2 mL/min, not 10.
- C: Above 2 mL/min the maximum clearance formula UV/P applies.
- D: The cut-off between the two formulas is 2 mL/min, not 0.5.
Question 2 · Medium
A 34-year-old woman has had no periods for 8 months, and her pregnancy test is negative. FSH 82 IU/L and LH 46 IU/L (follicular reference 3-10), estradiol low, prolactin and TSH normal. Where is the defect?
1. AEndometrium
2. BHypothalamus
3. CAnterior pituitary
4. DOvary
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Answer: D · Ovary
Low estradiol with very high FSH and LH shows that the pituitary is responding normally to absent ovarian feedback. The ovary is failing, which before age 40 is primary (premature) ovarian insufficiency. A pituitary or hypothalamic cause would give low or inappropriately normal gonadotrophins. An endometrial cause, such as intrauterine adhesions, leaves the hormones normal.
- A: An endometrial cause leaves FSH, LH and estradiol normal.
- B: A hypothalamic defect would give low or normal FSH and LH.
- C: A pituitary defect would give low FSH and LH.
Question 3 · Hard
A 23-year-old woman has had irregular periods since menarche, acne and excess facial hair; her BMI is 31 kg/m². Day 3 results: LH 16 IU/L and FSH 5 IU/L (both 3-10), total testosterone 82 ng/dL (15-70), prolactin and TSH normal, early-morning 17-hydroxyprogesterone 0.9 ng/mL (below 2). The most likely diagnosis is:
1. AAndrogen-secreting adrenal tumour
2. BNon-classic congenital adrenal hyperplasia
3. CPolycystic ovary syndrome
4. DHyperprolactinaemia
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Answer: C · Polycystic ovary syndrome
Long-standing irregular cycles, signs of androgen excess, obesity, an LH:FSH ratio above 2 and a mildly raised testosterone fit polycystic ovary syndrome. A normal early-morning 17-hydroxyprogesterone makes non-classic 21-hydroxylase deficiency unlikely. An androgen-secreting tumour gives rapidly progressive virilisation and a much higher testosterone or DHEAS. Prolactin is normal, which excludes hyperprolactinaemia.
- A: A tumour would give rapid virilisation and a much higher androgen level.
- B: A normal 17-hydroxyprogesterone argues against non-classic CAH.
- D: Prolactin is normal in this patient.
Question 4 · Hard
A 45-year-old man has recurrent duodenal and jejunal ulcers and chronic diarrhoea despite treatment. Off proton pump inhibitors: basal acid output 18 mmol/h (reference below 5), maximal acid output after pentagastrin 24 mmol/h, fasting serum gastrin 1,100 pg/mL (below 100). The most likely diagnosis is:
1. AAtrophic gastritis
2. BZollinger-Ellison syndrome
3. CPernicious anaemia
4. DCommon duodenal ulcer
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Answer: B · Zollinger-Ellison syndrome
The BAO/MAO ratio is 18/24 = 0.75. A ratio above 0.6 means the stomach is already secreting near its maximum at rest, as in a gastrin-secreting tumour, and the gastrin of 1,100 pg/mL confirms it. Ulcers beyond the duodenal bulb and diarrhoea from acid inactivating pancreatic enzymes are typical. Pernicious anaemia and atrophic gastritis also raise gastrin, but with little or no acid secretion.
- A: Atrophic gastritis raises gastrin with low, not high, acid output.
- C: Pernicious anaemia raises gastrin but causes achlorhydria.
- D: A common duodenal ulcer has a normal gastrin and a BAO/MAO ratio below 0.6.
Question 5 · Medium
A 40-year-old woman has weakness, weight loss and darkening of her skin creases. Basal plasma ACTH is high, and serum cortisol does not rise 30 or 60 minutes after 250 µg of tetracosactide. These results indicate:
1. APrimary adrenal insufficiency
2. BSuppression by long-term prednisolone
3. CEctopic ACTH secretion
4. DPituitary ACTH deficiency
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Answer: A · Primary adrenal insufficiency
A failed cortisol response to synthetic ACTH shows that the adrenal cortex cannot make cortisol. With a high basal ACTH, the fault is in the adrenal gland itself, Addison disease, and the excess ACTH (with related POMC peptides) darkens the skin. In pituitary deficiency or after long-term glucocorticoids, ACTH is low and there is no pigmentation. Ectopic ACTH secretion raises cortisol rather than leaving it low.
- B: Exogenous steroids suppress ACTH, so basal ACTH would be low.
- C: Ectopic ACTH drives cortisol high, causing Cushing syndrome.
- D: Pituitary ACTH deficiency gives a low ACTH and no pigmentation.
Question 6 · Medium
A patient with a metastatic carcinoid tumour and a very high urine 5-HIAA develops dermatitis and diarrhoea. Why?
1. AThe tumour consumes dietary riboflavin
2. BTryptophan is diverted from niacin to serotonin
3. C5-HIAA inactivates pyridoxal phosphate
4. DSerotonin blocks the absorption of thiamine
Answer and explanation in LearnFree account
Question 7 · Easy
In the Zimmermann reaction for urinary 17-ketosteroids, which reagent do they react with?
1. APhenylhydrazine in sulphuric acid
2. Bm-Dinitrobenzene in alkali
3. C1-Nitroso-2-naphthol
4. DDiazotised p-nitroaniline
Answer and explanation in LearnFree account
Question 8 · Medium
In cirrhosis of the liver, the albumin/globulin ratio is often reversed. The main reason is:
1. AThe biuret method overestimates globulins
2. BAlbumin is lost in urine while globulins are kept
3. CLess albumin is made while polyclonal gamma globulins rise
4. DGlobulins are concentrated by dehydration
Answer and explanation in LearnFree account
Question 9 · Hard
Overnight timed collection from a small woman (body surface area 1.38 m²): 720 mL passed in exactly 12 hours, creatinine 96 mg/dL in this urine and 1.2 mg/dL in her serum. What is her clearance normalised to 1.73 m²?
1. A50 mL/min
2. B80 mL/min
3. C100 mL/min
4. D64 mL/min
Answer and explanation in LearnFree account
Question 10 · Easy
Which enzyme iodinates tyrosine residues in thyroglobulin, the step blocked by carbimazole?
1. AThyroid peroxidase
2. BType 1 5'-deiodinase
3. CLysosomal protease
4. DIodotyrosine deiodinase
Answer and explanation in LearnFree account
Question 11 · Hard
A 28-year-old man has fever, nausea and jaundice. ALT 1,850 U/L and AST 1,320 U/L (below 40), ALP 160 U/L (40-130), total bilirubin 6.5 mg/dL with both fractions raised, and bilirubin and excess urobilinogen in the urine. The most likely diagnosis is:
1. AAlcoholic hepatitis
2. BAcute viral hepatitis
3. CHaemolytic jaundice
4. DExtrahepatic biliary obstruction
Answer and explanation in LearnFree account
Question 12 · Medium
In the secretin test of exocrine pancreatic function, the duodenal juice collected after secretin is analysed mainly for:
1. AVolume and bicarbonate concentration
2. BBilirubin and bile salt content
3. CTrypsin and chymotrypsin activity
4. DAmylase and lipase activity
Answer and explanation in LearnFree account
Question 13 · Hard
A woman with central obesity, purple striae and hypertension has a raised midnight cortisol. Plasma ACTH is 85 pg/mL (10-60), and high-dose (8 mg) dexamethasone lowers her morning cortisol by 70%. The most likely cause is:
1. ALong-term oral prednisolone intake
2. BAn adrenal cortical adenoma
3. CEctopic ACTH from a lung carcinoma
4. DA pituitary ACTH-secreting adenoma
Answer and explanation in LearnFree account
Question 14 · Medium
A woman on an oestrogen-containing contraceptive pill has a raised total T4, but her free T4 and TSH are normal. The reason is that oestrogen:
1. AStimulates the TSH receptor on the thyroid
2. BBlocks the conversion of T4 to T3
3. CRaises the level of thyroxine-binding globulin
4. DLowers the renal clearance of T4
Answer and explanation in LearnFree account
Question 15 · Easy
In a healthy person with a normal day-night routine, serum cortisol is highest at about:
1. ANoon, after the midday meal
2. B4 p.m., in the afternoon
3. CMidnight, soon after sleep
4. D8 a.m., soon after waking
Answer and explanation in LearnFree account
Question 16 · Easy
Which test is now regarded as the most sensitive single test to exclude phaeochromocytoma?
1. AUrinary homovanillic acid
2. BPlasma free metanephrines
3. C24-hour urinary VMA
4. DPlasma dopamine
Answer and explanation in LearnFree account
Question 17 · Hard
A 26-year-old woman has had no periods for 7 months and has milky nipple discharge. Pregnancy test negative, TSH 2.1 mIU/L (0.4-4.5), prolactin 180 ng/mL (below 25), on no medicines; LH and FSH low-normal. The most likely diagnosis is:
1. APrimary hypothyroidism
2. BPrimary ovarian failure
3. CProlactinoma
4. DPolycystic ovary syndrome
Answer and explanation in LearnFree account
Question 18 · Medium
A 38-year-old man has hypertension that needs three drugs and a serum potassium of 2.9 mmol/L. Which is the best screening test for the likely cause?
1. ASerum thyroid-stimulating hormone
2. BPlasma aldosterone to renin ratio
3. C24-hour urinary vanillylmandelic acid
4. DMidnight serum cortisol
Answer and explanation in LearnFree account
Question 19 · Medium
A patient's AST is 210 U/L and ALT 90 U/L (both below 40). An AST/ALT ratio above 2 like this points most to:
1. ANon-alcoholic fatty liver disease
2. BAlcoholic liver disease
3. CGallstone obstruction
4. DAcute viral hepatitis
Answer and explanation in LearnFree account
Question 20 · Medium
In the hippuric acid test, a dose of sodium benzoate is given and urinary hippuric acid is measured. This tests the liver's ability to:
1. AConjugate benzoate with glycine
2. BSynthesise plasma proteins
3. CExcrete dyes into the bile
4. DStore glycogen from glucose
Answer and explanation in LearnFree account
Question 21 · Easy
In a healthy young adult, the glomerular filtration rate measured by inulin clearance is about:
1. A12 mL/min per 1.73 m²
2. B120 mL/min per 1.73 m²
3. C1,200 mL/min per 1.73 m²
4. D650 mL/min per 1.73 m²
Answer and explanation in LearnFree account
Question 22 · Easy
In a child with recurrent chest infections, which sweat chloride result supports a diagnosis of cystic fibrosis?
1. ABelow 10 mmol/L
2. B30-59 mmol/L
3. C60 mmol/L or more
4. DBelow 30 mmol/L
Answer and explanation in LearnFree account
Question 23 · Medium
Before a 24-hour urine 5-HIAA test, the patient avoids bananas, pineapple, tomatoes and walnuts for a few days because these foods:
1. AContain serotonin and raise 5-HIAA falsely
2. BContain vanillin that reacts in the assay
3. CMake the urine alkaline and destroy 5-HIAA
4. DInhibit monoamine oxidase and lower 5-HIAA
Answer and explanation in LearnFree account
Question 24 · Hard
Three months after surgery for a pituitary macroadenoma, a man feels tired and cold. TSH 1.2 mIU/L (0.4-4.5), free T4 0.4 ng/dL (0.8-1.8), 8 a.m. cortisol 3 µg/dL (6-23). What is the most likely thyroid diagnosis?
1. ACentral (pituitary) hypothyroidism
2. BPrimary hypothyroidism from Hashimoto disease
3. CSubclinical hypothyroidism
4. DThyroid hormone resistance
Answer and explanation in LearnFree account
Question 25 · Medium
In pernicious anaemia, gastric analysis and serum gastrin typically show:
1. ANo acid, with a high serum gastrin
2. BHigh acid, with a high serum gastrin
3. CNo acid, with a low serum gastrin
4. DNormal acid, with a low serum gastrin
Answer and explanation in LearnFree account

23 more Organ function tests and hormones questions

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Organ function tests and hormones

In the Van Slyke urea clearance test, 'standard clearance' (U√V/P) replaces 'maximum clearance' (UV/P) when the urine flow is:

A 34-year-old woman has had no periods for 8 months, and her pregnancy test is negative. FSH 82 IU/L and LH 46 IU/L (follicular reference 3-10), estradiol low, prolactin and TSH normal. Where is the defect?

A 40-year-old woman has weakness, weight loss and darkening of her skin creases. Basal plasma ACTH is high, and serum cortisol does not rise 30 or 60 minutes after 250 µg of tetracosactide. These results indicate:

A patient with a metastatic carcinoid tumour and a very high urine 5-HIAA develops dermatitis and diarrhoea. Why?

In the Zimmermann reaction for urinary 17-ketosteroids, which reagent do they react with?

In cirrhosis of the liver, the albumin/globulin ratio is often reversed. The main reason is:

Overnight timed collection from a small woman (body surface area 1.38 m²): 720 mL passed in exactly 12 hours, creatinine 96 mg/dL in this urine and 1.2 mg/dL in her serum. What is her clearance normalised to 1.73 m²?

Which enzyme iodinates tyrosine residues in thyroglobulin, the step blocked by carbimazole?

A 28-year-old man has fever, nausea and jaundice. ALT 1,850 U/L and AST 1,320 U/L (below 40), ALP 160 U/L (40-130), total bilirubin 6.5 mg/dL with both fractions raised, and bilirubin and excess urobilinogen in the urine. The most likely diagnosis is:

In the secretin test of exocrine pancreatic function, the duodenal juice collected after secretin is analysed mainly for:

A woman with central obesity, purple striae and hypertension has a raised midnight cortisol. Plasma ACTH is 85 pg/mL (10-60), and high-dose (8 mg) dexamethasone lowers her morning cortisol by 70%. The most likely cause is:

A woman on an oestrogen-containing contraceptive pill has a raised total T4, but her free T4 and TSH are normal. The reason is that oestrogen:

In a healthy person with a normal day-night routine, serum cortisol is highest at about:

Which test is now regarded as the most sensitive single test to exclude phaeochromocytoma?

A 26-year-old woman has had no periods for 7 months and has milky nipple discharge. Pregnancy test negative, TSH 2.1 mIU/L (0.4-4.5), prolactin 180 ng/mL (below 25), on no medicines; LH and FSH low-normal. The most likely diagnosis is:

A 38-year-old man has hypertension that needs three drugs and a serum potassium of 2.9 mmol/L. Which is the best screening test for the likely cause?

A patient's AST is 210 U/L and ALT 90 U/L (both below 40). An AST/ALT ratio above 2 like this points most to:

In the hippuric acid test, a dose of sodium benzoate is given and urinary hippuric acid is measured. This tests the liver's ability to:

In a healthy young adult, the glomerular filtration rate measured by inulin clearance is about:

In a child with recurrent chest infections, which sweat chloride result supports a diagnosis of cystic fibrosis?

Before a 24-hour urine 5-HIAA test, the patient avoids bananas, pineapple, tomatoes and walnuts for a few days because these foods:

Three months after surgery for a pituitary macroadenoma, a man feels tired and cold. TSH 1.2 mIU/L (0.4-4.5), free T4 0.4 ng/dL (0.8-1.8), 8 a.m. cortisol 3 µg/dL (6-23). What is the most likely thyroid diagnosis?

In pernicious anaemia, gastric analysis and serum gastrin typically show: