A 58-year-old woman told to take a 60,000 IU cholecalciferol sachet once a week has been taking one every day for four months. She now has vomiting, constipation, polyuria and confusion. Serum calcium is 13.6 mg/dL, PTH is suppressed and serum 25-hydroxyvitamin D is 240 ng/mL (sufficiency 30-100). What is the most likely cause of her hypercalcaemia?

Humoral hypercalcaemia of malignancy

Vitamins and minerals: deficiency and toxicity

26 NEET-PG practice questions on Vitamins and minerals: deficiency and toxicity, 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
A 48-year-old man with chronic alcohol use is brought to casualty confused, with an unsteady gait and nystagmus with lateral rectus palsy. He became worse after an infusion of 25% dextrose. Low activity of which red cell enzyme would confirm the vitamin deficiency?
1. APyruvate carboxylase
2. BTransketolase
3. CAspartate aminotransferase
4. DGlutathione reductase
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Answer: B · Transketolase
Confusion, ataxia and ophthalmoplegia in an alcoholic is Wernicke encephalopathy from thiamine deficiency. Thiamine pyrophosphate is the coenzyme for transketolase in the pentose phosphate pathway, and also for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase. A low red cell transketolase activity that rises when TPP is added confirms deficiency. Glucose given without thiamine uses up the remaining thiamine and can precipitate or worsen Wernicke encephalopathy, so IV thiamine should come first.
- A: Pyruvate carboxylase needs biotin, not thiamine, and is not a red cell test.
- C: Red cell aminotransferase activity assesses pyridoxine (B6) status.
- D: Red cell glutathione reductase activity assesses riboflavin (B2) status.
Question 2 · Hard
A 50-year-old man has taken high-dose zinc tablets, bought online for immunity, for 10 months. He has numb feet, an unsteady gait worse in the dark, and reduced vibration and joint position sense in the legs. Hb 8.6 g/dL, MCV 102 fL, neutrophils 900/µL, serum B12 and folate normal, and serum zinc high. Deficiency of which element explains his illness?
1. AManganese
2. BSelenium
3. CMolybdenum
4. DCopper
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Answer: D · Copper
Excess zinc induces metallothionein in enterocytes, which binds dietary copper more strongly than zinc and is shed with the cells, so copper absorption falls. Copper deficiency causes anaemia, neutropenia and a myelopathy that mimics subacute combined degeneration from B12 deficiency, because copper enzymes such as cytochrome oxidase are needed for myelin and blood cell production. Serum copper and ceruloplasmin are low. Stopping zinc and replacing copper corrects the blood counts, but the neurological damage may recover only partly.
- A: Manganese is not depleted by zinc excess; its toxicity causes parkinsonism.
- B: Selenium deficiency causes cardiomyopathy and myopathy, not anaemia with myelopathy.
- C: Molybdenum deficiency is very rare and causes sulfite toxicity.
Question 3 · Medium
A 64-year-old woman with pernicious anaemia has numbness of both feet and a positive Romberg sign. Consider four statements: 1. Methylmalonyl-CoA mutase needs adenosylcobalamin as its cofactor. 2. Folic acid alone could improve her anaemia while the neurological damage progresses. 3. Methionine synthase needs methylcobalamin. 4. Her plasma homocysteine is expected to be normal. Which statements are correct?
1. A1 and 2 only
2. B3 and 4 only
3. C1, 3 and 4 only
4. D1, 2 and 3 only
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Answer: D · 1, 2 and 3 only
Vitamin B12 has two coenzyme forms in humans: adenosylcobalamin for methylmalonyl-CoA mutase and methylcobalamin for methionine synthase. Lack of methionine synthase activity traps folate as methyl-tetrahydrofolate and raises homocysteine, so statement 4 is false. Large doses of folic acid can bypass the trap and correct the anaemia but not the myelin damage, which is linked to methylmalonyl-CoA accumulation and reduced S-adenosylmethionine. She needs lifelong intramuscular B12.
- A: Omits statement 3; methionine synthase does need methylcobalamin.
- B: Includes statement 4 and omits 1 and 2; homocysteine is raised, not normal.
- C: Includes statement 4 and omits 2, the danger of giving folic acid alone.
Question 4 · Medium
A 58-year-old woman told to take a 60,000 IU cholecalciferol sachet once a week has been taking one every day for four months. She now has vomiting, constipation, polyuria and confusion. Serum calcium is 13.6 mg/dL, PTH is suppressed and serum 25-hydroxyvitamin D is 240 ng/mL (sufficiency 30-100). What is the most likely cause of her hypercalcaemia?
1. APrimary hyperparathyroidism
2. BHumoral hypercalcaemia of malignancy
3. CVitamin D toxicity
4. DSarcoidosis
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Answer: C · Vitamin D toxicity
Very high 25(OH)D with suppressed PTH in someone taking large daily doses of cholecalciferol is vitamin D intoxication, increasingly seen in India with over-the-counter sachets and injections. Excess vitamin D raises calcium absorption from the gut and bone resorption, causing hypercalcaemia, hypercalciuria and sometimes kidney injury. Because vitamin D is stored in fat, toxicity can last for months after the drug is stopped. Treatment is stopping vitamin D and calcium, IV saline, and if needed bisphosphonates or steroids.
- A: Primary hyperparathyroidism has a high or inappropriately normal PTH, not a suppressed one.
- B: PTHrP-driven hypercalcaemia does not raise 25(OH)D, and there is no history of cancer.
- D: Sarcoidosis raises 1,25(OH)2D from granulomas but does not give a very high 25(OH)D.
Question 5 · Medium
A 52-year-old man has fatigue and a smooth tongue. Hb 8.9 g/dL, MCV 112 fL, hypersegmented neutrophils on the smear; serum B12 is 210 pg/mL (borderline) and red cell folate is normal. He has no neurological signs yet. Which raised result would best confirm vitamin B12 deficiency at the tissue level?
1. ASerum homocysteine
2. BSerum methylmalonic acid
3. CSerum indirect bilirubin
4. DSerum lactate dehydrogenase
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Answer: B · Serum methylmalonic acid
Adenosylcobalamin is the cofactor of methylmalonyl-CoA mutase, which converts methylmalonyl-CoA to succinyl-CoA. In B12 deficiency, methylmalonic acid accumulates, whereas folate deficiency leaves it normal, so a raised MMA confirms B12 deficiency when the serum B12 is borderline. Homocysteine rises in both B12 and folate deficiency because methionine synthase needs both. Confirming B12 deficiency matters because folic acid alone does not prevent its neurological damage.
- A: Homocysteine is raised in both B12 and folate deficiency, so it does not separate them.
- C: Indirect bilirubin rises from intramedullary haemolysis in any megaloblastic anaemia.
- D: LDH rises in any megaloblastic anaemia from ineffective erythropoiesis.
Question 6 · Medium
A 56-year-old woman from a hilly district of Uttarakhand has had a large multinodular goitre for 20 years and was euthyroid last year. Three weeks after a contrast-enhanced CT abdomen, she develops palpitations, weight loss and tremor; TSH is suppressed and free T4 is high. What is the most likely explanation?
1. AIodine-induced hyperthyroidism
2. BGraves disease
3. CSubacute thyroiditis
4. DWolff-Chaikoff effect
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Question 7 · Medium
A 9-year-old boy from a sub-Himalayan village in an area of severe iodine deficiency is examined during a school health survey. He is deaf and mute, has a squint, spastic weakness of both legs and severe intellectual disability. His height is normal for age, and he is clinically euthyroid. Which form of iodine deficiency disorder is this?
1. AMyxoedematous cretinism
2. BNeurological cretinism
3. CIodine-induced thyroiditis
4. DAcquired juvenile hypothyroidism
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Question 8 · Medium
A 3-month-old exclusively breastfed baby from a family that eats mainly polished rice is brought to a district hospital with a weak, hoarse cry that has become almost silent, vomiting, restlessness and breathlessness. The liver is enlarged and the heart rate is 180/min. The mother, who followed a restricted diet after delivery, has numbness of both feet. Which treatment is most urgent?
1. AIntravenous calcium gluconate
2. BIntramuscular vitamin B12
3. CParenteral thiamine to the baby
4. DOral riboflavin to mother and baby
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Question 9 · Medium
An 18-month-old girl in a slum in Kolkata, breastfed and rarely taken outdoors, has widened wrists, a beaded swelling of the costochondral junctions and bowed legs. X-ray of the wrist shows cupping and fraying of the metaphysis. Which set of results is most likely?
1. ANormal phosphate, low ALP, low PTH, normal 25(OH)D
2. BLow phosphate, high ALP, normal PTH, normal 25(OH)D
3. CHigh phosphate, high ALP, high PTH, normal 25(OH)D
4. DLow phosphate, high ALP, high PTH, low 25(OH)D
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Question 10 · Easy
A 2-year-old boy is brought to casualty two hours after swallowing many of his pregnant mother's iron tablets. He has vomited blood-stained material and has diarrhoea, and his serum iron is markedly raised. Which antidote should be given?
1. ACalcium disodium edetate
2. BDimercaprol
3. CDesferrioxamine
4. DD-penicillamine
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Question 11 · Medium
A 35-year-old software engineer from Chennai has had loose, bulky stools, weight loss and fatigue for five months. He has lived in Chennai all his life. Hb 9.2 g/dL, MCV 114 fL, red cell folate low, B12 normal. Small bowel biopsy shows partial villous atrophy, and anti-tissue transglutaminase antibodies are negative. Stool tests show no parasites. What is the most appropriate treatment?
1. AGluten-free diet for life
2. BFolic acid with tetracycline
3. CPancreatic enzyme replacement
4. DOral metronidazole alone
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Question 12 · Medium
A 47-year-old man with long-standing heavy alcohol use and poor diet is admitted with vomiting. Arterial pH is 7.26, bicarbonate 13 mmol/L, lactate 7.5 mmol/L (reference 0.5-2.2) and glucose 92 mg/dL; there is no shock or sepsis. The lactate falls quickly after intravenous thiamine. Which enzyme's reduced activity explains the lactic acidosis?
1. APyruvate dehydrogenase
2. BPyruvate carboxylase
3. CPhosphoenolpyruvate carboxykinase
4. DLactate dehydrogenase
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Question 13 · Medium
A 10-month-old boy is brought with vomiting, irritability and poor feeding for a week. The anterior fontanelle is bulging and tense; there is no fever, neck stiffness or focal deficit, and CSF is normal apart from a high opening pressure. His grandmother has been giving him a daily spoon of an over-the-counter oil, and he also received doses at two different health camps. Excess of which vitamin is most likely?
1. AVitamin A
2. BVitamin E
3. CVitamin D
4. DVitamin K
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Question 14 · Medium
A 10-year-old boy has a red, scaly rash on his face and arms after sun exposure and episodes of unsteady gait. His parents are first cousins. Urine chromatography shows large amounts of neutral amino acids, including tryptophan, with normal plasma amino acid levels. What is the underlying defect?
1. APhenylalanine hydroxylase
2. BA neutral amino acid transporter
3. CKynureninase of tryptophan breakdown
4. DA cystine and dibasic amino acid transporter
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Question 15 · Hard
A 48-year-old woman with rheumatoid arthritis for 10 years has been taking diclofenac most days. Hb 9.4 g/dL, MCV 74 fL, CRP 38 mg/L, serum iron low, TIBC low-normal, transferrin saturation 8%, serum ferritin 85 ng/mL, and soluble transferrin receptor is markedly raised. What is the best interpretation?
1. ASideroblastic anaemia
2. BIron deficiency with anaemia of chronic disease
3. CAnaemia of chronic disease alone
4. DBeta-thalassaemia trait
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Question 16 · Hard
A 63-year-old strict vegetarian from Gujarat had an inguinal hernia repair under general anaesthesia with nitrous oxide for 2 hours. Four weeks later he has tingling in both hands and feet and an unsteady gait, with loss of vibration sense and a positive Romberg sign. MCV is 104 fL and serum B12 is low-normal. How did the anaesthetic precipitate his illness?
1. AIt oxidises the cobalt of cobalamin
2. BIt inhibits dihydrofolate reductase
3. CIt blocks intrinsic factor secretion
4. DIt increases renal loss of cobalamin
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Question 17 · Medium
A 3-year-old boy has rickets that did not improve after two courses of high-dose cholecalciferol. Serum calcium 7.6 mg/dL, phosphate 2.6 mg/dL, ALP raised, PTH raised, 25-hydroxyvitamin D normal and 1,25-dihydroxyvitamin D low. Kidney function is normal. Which treatment is most appropriate?
1. AA higher dose of cholecalciferol
2. BCalcifediol alone
3. COral phosphate with calcitriol only
4. DCalcitriol with calcium
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Question 18 · Hard
A 40-year-old man has been on total parenteral nutrition for 3 weeks after an intestinal fistula; the hospital ran out of the multivitamin additive two weeks ago. He develops tachycardia, warm peripheries, hypotension and a worsening metabolic acidosis with lactate 9 mmol/L. Blood cultures are negative and the abdomen is soft. What is the next best step?
1. AStart empirical meropenem
2. BIntravenous thiamine at once
3. CIntravenous sodium bicarbonate
4. DUrgent CT angiography of the mesentery
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Question 19 · Easy
A 7-week-old baby girl, born at home and exclusively breastfed, is brought to casualty with vomiting, a bulging fontanelle and a seizure. CT shows an intracranial haemorrhage. PT and aPTT are both prolonged, and the platelet count is normal. She received no injection at birth. What is the most likely diagnosis?
1. AImmune thrombocytopenic purpura
2. BLate vitamin K deficiency bleeding
3. CHaemophilia A
4. DVon Willebrand disease
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Question 20 · Medium
A 66-year-old man in the ICU has received intravenous ceftriaxone and nothing by mouth for 18 days after bowel surgery. He now oozes from cannula sites; PT is prolonged, platelets and fibrinogen are normal, and the PT corrects with intravenous vitamin K. Which post-translational modification of clotting factors was impaired?
1. APhosphorylation of tyrosine residues
2. BHydroxylation of proline residues
3. CGamma-carboxylation of glutamate residues
4. DGlycosylation of asparagine residues
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Question 21 · Easy
A 42-year-old farmer from a village in Telangana whose staple is jowar (sorghum) has a dark, scaly rash on his forearms and neck after sun exposure, chronic diarrhoea and poor memory. His diet contains enough tryptophan. Which amino acid in his staple is thought to interfere with niacin synthesis?
1. AMethionine
2. BLeucine
3. CThreonine
4. DLysine
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Question 22 · Medium
A 26-year-old man in Tamil Nadu ate a rat-killer paste five days ago after a family quarrel; the packet says it contains bromadiolone. He now has gum bleeding and haematuria. INR is 9.2, platelets are normal and liver enzymes are normal. Besides fresh frozen plasma, what is the key treatment?
1. AProtamine sulfate infusion
2. BVitamin K1 in high doses for weeks
3. CA single dose of vitamin K1
4. DOral menadione for three days
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Question 23 · Easy
A 7-month-old boy, recently weaned from breast milk to diluted cow's milk, has red, crusted, erosive patches around the mouth, nose and anus and on his hands and feet, with diarrhoea, patchy hair loss and irritability. Serum alkaline phosphatase is low for his age. Deficiency of which mineral is most likely?
1. AZinc
2. BMagnesium
3. CSelenium
4. DCopper
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Question 24 · Medium
A 20-year-old college student with severe nodulocystic acne is to start oral isotretinoin in the dermatology OPD. The doctor plans her counselling with four points: 1. She must use effective contraception from before treatment until one month after stopping. 2. A negative pregnancy test is needed before starting. 3. She may donate blood while on treatment. 4. She should avoid vitamin A supplements during treatment. Which points are correct?
1. A1 and 3 only
2. B2 and 4 only
3. C1, 2 and 4 only
4. D1, 2 and 3 only
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Question 25 · Easy
A 30-year-old migrant labourer from coastal Odisha who eats mainly polished rice and drinks heavily has breathlessness and swollen legs for two weeks. Pulse is 116/min and bounding, the extremities are warm, the JVP is raised and the heart is enlarged. His symptoms resolve within days of a vitamin injection. Which vitamin was deficient?
1. ANiacin
2. BRiboflavin
3. CThiamine
4. DAscorbic acid
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Vitamins and minerals: deficiency and toxicity

A 48-year-old man with chronic alcohol use is brought to casualty confused, with an unsteady gait and nystagmus with lateral rectus palsy. He became worse after an infusion of 25% dextrose. Low activity of which red cell enzyme would confirm the vitamin deficiency?

An 18-month-old girl in a slum in Kolkata, breastfed and rarely taken outdoors, has widened wrists, a beaded swelling of the costochondral junctions and bowed legs. X-ray of the wrist shows cupping and fraying of the metaphysis. Which set of results is most likely?

A 2-year-old boy is brought to casualty two hours after swallowing many of his pregnant mother's iron tablets. He has vomited blood-stained material and has diarrhoea, and his serum iron is markedly raised. Which antidote should be given?

A 10-year-old boy has a red, scaly rash on his face and arms after sun exposure and episodes of unsteady gait. His parents are first cousins. Urine chromatography shows large amounts of neutral amino acids, including tryptophan, with normal plasma amino acid levels. What is the underlying defect?

A 3-year-old boy has rickets that did not improve after two courses of high-dose cholecalciferol. Serum calcium 7.6 mg/dL, phosphate 2.6 mg/dL, ALP raised, PTH raised, 25-hydroxyvitamin D normal and 1,25-dihydroxyvitamin D low. Kidney function is normal. Which treatment is most appropriate?

A 42-year-old farmer from a village in Telangana whose staple is jowar (sorghum) has a dark, scaly rash on his forearms and neck after sun exposure, chronic diarrhoea and poor memory. His diet contains enough tryptophan. Which amino acid in his staple is thought to interfere with niacin synthesis?

A 26-year-old man in Tamil Nadu ate a rat-killer paste five days ago after a family quarrel; the packet says it contains bromadiolone. He now has gum bleeding and haematuria. INR is 9.2, platelets are normal and liver enzymes are normal. Besides fresh frozen plasma, what is the key treatment?