Hormones and their estimation

24 Kerala PSC Lab Technician Gr II practice questions on Hormones and their estimation, part of Biochemistry. The first 24 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   Which hormone acts on its target cells through cyclic AMP as the second messenger?

   1. ACortisol
   2. BThyroxine
   3. CGlucagon
   4. DEstradiol

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   Answer: C · Glucagon

   Glucagon is a peptide that cannot cross the cell membrane, so it binds a G-protein-coupled receptor on the liver cell surface. This activates adenylate cyclase, and the cyclic AMP formed switches on protein kinase A, which drives glycogen breakdown. Steroid and thyroid hormones are lipid-soluble, enter the cell and act through intracellular receptors that change gene transcription. Peptide hormones therefore act within minutes, steroid hormones over hours.

   • A: Cortisol is a steroid that binds an intracellular receptor.
   • B: Thyroxine enters the cell and acts through a nuclear receptor.
   • D: Estradiol is a steroid that acts through an intracellular receptor.

2. Question 2 · Medium

   In a competitive radioimmunoassay, which result goes with a higher hormone concentration in the patient's sample?

   1. ANo change in bound or free counts
   2. BMore counts in the bound fraction
   3. CFewer counts in the bound fraction
   4. DFewer counts in the free fraction

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   Answer: C · Fewer counts in the bound fraction

   In competitive RIA, a fixed amount of radiolabelled hormone competes with the patient's unlabelled hormone for a limited number of antibody sites. The more hormone the patient has, the more labelled hormone is pushed off the antibody into the free fraction. Bound counts therefore fall as concentration rises, and the standard curve slopes downward. In a sandwich (immunometric) assay the signal rises with concentration instead.

   • A: The bound and free counts both shift whenever the hormone level changes.
   • B: More bound counts mean less patient hormone in a competitive assay.
   • D: Displaced labelled hormone adds to the free fraction, so free counts rise.

3. Question 3 · Hard

   A 28-year-old woman taking an estrogen-containing oral contraceptive has a high 8 am serum total cortisol. Her 24-hour urinary free cortisol is normal and she has no features of Cushing syndrome. What best explains these results?

   1. ACortisol-secreting adrenal adenoma
   2. BRaised cortisol-binding globulin
   3. CReduced renal clearance of cortisol
   4. DCross-reaction of estrogen in the assay

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   Answer: B · Raised cortisol-binding globulin

   Estrogen makes the liver produce more cortisol-binding globulin (transcortin), so more cortisol circulates bound to protein. Serum total cortisol rises, but the free, active cortisol stays normal. Urinary free cortisol reflects the free fraction, so it is normal, which fits the absence of Cushing features. Estrogen-containing drugs are therefore stopped for several weeks before serum cortisol testing, or a free cortisol measure is used.

   • A: An adenoma would raise urinary free cortisol and cause Cushing features.
   • C: Cortisol is cleared mainly by the liver; the kidney does not set its serum level.
   • D: Estrogen does not cross-react significantly in cortisol immunoassays.

4. Question 4 · Easy

   All of the following hormones are secreted by the anterior pituitary EXCEPT:

   1. AProlactin
   2. BOxytocin
   3. CGrowth hormone
   4. DACTH

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   Answer: B · Oxytocin

   Oxytocin and antidiuretic hormone are made in the supraoptic and paraventricular nuclei of the hypothalamus. They travel down nerve axons and are stored in, and released from, the posterior pituitary. The anterior pituitary secretes growth hormone, prolactin, TSH, ACTH, FSH and LH. Its secretion is controlled by releasing and inhibiting hormones carried in the portal blood from the hypothalamus.

   • A: Prolactin is made by the lactotroph cells of the anterior pituitary.
   • C: Growth hormone is made by the somatotroph cells of the anterior pituitary.
   • D: ACTH is cut from pro-opiomelanocortin in the anterior pituitary.

5. Question 5 · Medium

   A 25-year-old diabetic on insulin injections needs an assessment of his remaining beta-cell function. Which test is best?

   1. AFasting plasma glucose
   2. BSerum insulin
   3. CGlycated hemoglobin (HbA1c)
   4. DSerum C-peptide

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   Answer: D · Serum C-peptide

   Beta cells split proinsulin into insulin and C-peptide in equal amounts, so C-peptide reflects the patient's own insulin secretion. Injected insulin contains no C-peptide and does not interfere with its measurement. A serum insulin result would include the injected insulin, and insulin antibodies can disturb the assay. The same principle detects secret insulin injection as a cause of hypoglycemia: high insulin with low C-peptide.

   • A: Fasting glucose depends on the insulin dose and diet, not only on beta cells.
   • B: A serum insulin result includes the insulin he injects.
   • C: HbA1c shows average glucose over 2-3 months, not beta-cell output.

6. Question 6 · Medium

   Pregnancy tests use antibodies against the beta subunit of hCG, not the alpha subunit. Why?

   1. AThe alpha subunit is shared with LH, FSH and TSH
   2. BThe alpha subunit appears only after 12 weeks
   3. CThe alpha subunit is destroyed by urinary acid
   4. DOnly the beta subunit is excreted in urine

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7. Question 7 · Easy

   Calcitonin, the hormone that lowers serum calcium, is secreted by:

   1. AFollicular cells of the thyroid
   2. BChief cells of the parathyroid
   3. CParafollicular (C) cells of the thyroid
   4. DOxyphil cells of the parathyroid

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8. Question 8 · Hard

   An obese 32-year-old woman with acanthosis nigricans has fasting glucose 96 mg/dL and fasting insulin 1.5 µU/mL (reference 2-25 µU/mL). The sample reached the laboratory grossly hemolysed after a 5-hour delay. A fresh, unhemolysed repeat gives 34 µU/mL. What best explains the first result?

   1. AHigh-dose hook effect in the immunoassay
   2. BBeta-cell failure of type 1 diabetes
   3. CProlonged fasting before the first sample
   4. DInsulin destroyed by red cell proteases

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9. Question 9 · Medium

   The insulin receptor passes its signal into the cell mainly through:

   1. AAdenylate cyclase and cyclic AMP
   2. BA nuclear receptor that binds DNA
   3. CTyrosine kinase activity of the receptor
   4. DA ligand-gated calcium channel

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10. Question 10 · Easy

    All of the following hormones are synthesized from the amino acid tyrosine EXCEPT:

    1. AAdrenaline
    2. BMelatonin
    3. CDopamine
    4. DThyroxine

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11. Question 11 · Hard

    A 30-year-old woman had a severe postpartum hemorrhage 6 months ago and could not breastfeed. She now has tiredness and cold intolerance. TSH is 0.3 µIU/mL (0.4-4.0) and free T4 0.5 ng/dL (0.8-1.8). The most likely diagnosis is:

    1. APrimary hypothyroidism
    2. BGraves disease
    3. CSubclinical hyperthyroidism
    4. DSecondary hypothyroidism

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12. Question 12 · Hard

    A 42-year-old woman has weight gain, purple striae and hypertension. Her 24-hour urinary free cortisol is high and cortisol is not suppressed by 1 mg overnight dexamethasone. Plasma ACTH is raised, and 8 mg dexamethasone lowers her cortisol by more than 50%. The most likely cause is:

    1. ALong-term oral prednisolone
    2. BACTH-secreting pituitary adenoma
    3. CCortisol-secreting adrenal adenoma
    4. DEctopic ACTH from a lung tumour

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13. Question 13 · Easy

    Steroid hormones such as cortisol act on their target cells by binding to receptors located:

    1. AInside the cell
    2. BOn the cell membrane
    3. CIn the extracellular matrix
    4. DOn the outer mitochondrial membrane

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14. Question 14 · Easy

    Excess growth hormone secretion that begins after the epiphyses have fused causes:

    1. ACretinism
    2. BDwarfism
    3. CAcromegaly
    4. DGigantism

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15. Question 15 · Hard

    A clinically well 40-year-old man taking 10 mg biotin daily for hair loss has TSH below 0.01 µIU/mL and a high free T4. The laboratory uses streptavidin-biotin immunoassays for both. What is the best next step?

    1. AReport the results as Graves disease
    2. BRepeat after stopping biotin for some days
    3. CDilute the sample and repeat the TSH test
    4. DRepeat both tests at once on the same analyzer

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16. Question 16 · Easy

    Deficiency of antidiuretic hormone (vasopressin) causes:

    1. ADiabetes insipidus
    2. BAddison disease
    3. CSIADH
    4. DDiabetes mellitus

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17. Question 17 · Medium

    A 45-year-old woman has TSH 18 µIU/mL (reference 0.4-4.0) and free T4 0.5 ng/dL (reference 0.8-1.8). These results indicate:

    1. ASecondary hypothyroidism
    2. BSubclinical hypothyroidism
    3. CPrimary hyperthyroidism
    4. DPrimary hypothyroidism

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18. Question 18 · Medium

    Large hormones such as TSH are measured by a sandwich immunoassay, but T4 and steroids by a competitive one. Why?

    1. ASmall molecules cannot bind two antibodies at once
    2. BSmall molecules are present in higher amounts
    3. CCompetitive assays need no antibody
    4. DSandwich assays work only on urine

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19. Question 19 · Medium

    Urinary 17-ketosteroids, an index of androgen production, are estimated by the Zimmermann reaction. Which reagent reacts with them?

    1. Am-Dinitrobenzene in alkali
    2. BFerric chloride in acid
    3. CPhenylhydrazine in sulfuric acid
    4. DQuinol in sulfuric acid

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20. Question 20 · Easy

    Parathyroid hormone raises serum calcium and has which effect on serum phosphate?

    1. AIt lowers serum phosphate
    2. BIt doubles serum phosphate
    3. CIt raises serum phosphate
    4. DIt leaves phosphate unchanged

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21. Question 21 · Easy

    Estimation of vanillylmandelic acid (VMA) in a 24-hour urine sample helps to diagnose:

    1. AAddison disease
    2. BCushing syndrome
    3. CPheochromocytoma
    4. DCarcinoid syndrome

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22. Question 22 · Medium

    A 35-year-old woman has weakness, low blood pressure and darkening of the skin and gums. Serum sodium is 126 mEq/L and potassium 6.0 mEq/L. Which disorder is most likely?

    1. AConn syndrome
    2. BAddison disease
    3. CPheochromocytoma
    4. DCushing syndrome

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23. Question 23 · Medium

    Blood for serum cortisol is normally drawn at about 8 am. Why is the time of collection important?

    1. ACortisol has a diurnal rhythm
    2. BCortisol is unstable after noon
    3. CFood intake destroys cortisol
    4. DCortisol is released only at night

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24. Question 24 · Easy

    Which thyroid hormone is the most active at the tissue level?

    1. AThyroglobulin
    2. BThyroxine (T4)
    3. CReverse T3
    4. DTriiodothyronine (T3)

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