CSGD Quiz 4 2008

1

Which one of the following statements regarding lactation is correct?


  Lactation is stimulated by a neuroendocrine reflex.

  A decrease in progesterone levels is the only requirement for initiation of lactation.

  In the non-pregnant state, mammary alveoli are never secretory.

  Oxytocin and prolactin are released from the anterior pituitary.

  Prolactin stimulates milk production from the myoepithelial cells.


A is correct: Suckling stimulates the hypothalamus, which stimulates the pituitary gland to produce oxytocin and prolactin, the main hormones of lactation. B is incorrect: A decrease in oestradiol is also required. C is incorrect: Oestrogen usually inhibits the action of prolactin, preventing mammary alveoli secretion. The exception is the post-partum period when hormonal balance shifts in favour of the action of prolactin and oxytocin. D is incorrect: Oxytocin is released from the posterior pituitary. E is incorrect: Milk is produced from the mammary alveoli cells. Myoepithelial cell contraction is responsible for milk release.

2

With regard to Pit-1, which one of the following statements is correct?


  Pit-1 is an extra-cellular membrane receptor.

  Pit-1 regulates expression of growth hormone and ACTH in the anterior pituitary.

  Pit-1 is a nuclear transcription factor.

  Somatic mutations in the Pit-1 gene are found in one-third of growth hormone producing adenomas.

  Homozygous germ-line mutations in the Pit-1 gene are incompatible with life.


A is incorrect: Pit-1 is a an intracellular transcription factor. B is incorrect: It regulates growth hormone and prolactin via its distribution during development. C is correct. D is incorrect: A third of growth hormone producing adenomas are thought to be due to defective intrinsic GTPase activity. E is incorrect: Pit-1 is one of the 'master genes' of the pituitary, involved in regulating the production of GH and prolactin primarily. Abnormalities in the production of these hormones is not necessarily incompatible with life.

3

With regard to the anti-diuretic hormone (ADH), which one of the following statements is correct?


  It is synthesized in the posterior pituitary.

  It is a peptide hormone consisting of α and β sub-units.

  Reduced blood osmolarity releases ADH.

  ADH acts on proximal tubule of kidney.

  Deficiency of ADH is more likely with a craniopharyngioma than with a prolactinoma.


A is incorrect: It is released by the posterior pituitary, but synthesised in the hypothalamus. B is incorrect: ADH is a tri-peptide hormone (small) C is incorrect: Reduced blood osmolarity should result in a decrease in ADH. D is incorrect: ADH acts on the distal tubule. E is correct: Craniopharngiomas arise from cells of the pituitary stalk, and are therefore more likely to affect posterior pituitary secretions.

4

A 46 year-old nurse has a swelling in the anterior neck region that moves up and down on swallowing. The most likely diagnosis is a thyroid mass and the movement occurs because the thyroid gland is intimately related to


  The investing layer of cervical fascia.

  The prevertebral fascia.

  The pretracheal fascia.

  The carotid sheath.

  The superficial fascia.

5

After experiencing a difficult labour with her second child, a 32 year-old woman complains of urinary incontinence characterized by leaking of urine when intra-abdominal pressure is raised. The most likely cause for this is damage to


  Pubococcygeus.

  Iliococcygeus.

  Ischiococcygeus.

  Piriformis.

  Obturator internus.


Pubococcygeus is the pelvic floor muscle surrounding the bladder.

6

Which one of the following conditions is most likely to cause suppressed TSH levels?


  Pituitary tumour.

  Primary hypothyroidism.

  Thyroid hormone resistance syndrome.

  Clinical thyrotoxicosis.

  Cretinism.


A is incorrect: A functional pituitary tumour would increase TSH levels (although TSH functional adenomas are rare) B is incorrect: This would cause an increase in TSH levels as the pituitary tries to stimulate the thyroid. C is incorrect: As for B D is correct: Thyrotoxicosis is the state of increased thyroid hormones in the blood. Negative feedback would lead to a decrease in TSH levels. E is incorrect: Cretinism is caused by prenatal maternal hypothyroidism.

7

Which one of the following explains why many luteinizing hormone (LH) immunoassays do not discriminate between LH and human chorionic gonadotrophin (hCG)?


  They have the same alpha-subunits.

  They have the same beta-subunits.

  They have very similar beta-subunits.

  They are both glyco-proteins.

  They both have metabolic end-products which are measured in the assay.


A is incorrect: This is true of all the glycoprotein hormones (LH, FSH, hCG, TSH). B is incorrect: Each has a specific β-subunit C is correct: Antibody cross-binding is more likely to occur because of this. D is incorrect: This is true, but is not the reason for non-discrimination. E is incorrect: Immunoassays do not measure metabolic end-products.

8

Which one of the following statements regarding testosterone, or its activated product dihydrotestosterone, is NOT correct?


  It is the most potent of the 3 major androgens testosterone, androstenedione and dehydroepiandrosterone.

  It is largely bound to sex hormone binding globulin in the circulation.

  Only the free hormone is biologically active.

  There is a diurnal variation in its secretion.

  It is produced by the Sertoli cells in the testis.


A is correct: Testosterone is the most potent androgen (DHT more potent in some tissues). B is correct. C is correct. D is correct: Secretion responds to pulsatile gonadotrophin release. E is incorrect: Testosterone is produced in the Leydig cells (Sertoli cells are responsible for spermatogenesis).

9

The main mechanism of steroid hormone action is via:


  Cyclic AMP.

  ACTH.

  Modulating gene expression.

  Interaction with mitochondria.

  Intracellular calcium.

10

Excessive secretion of cortisol by the adrenal cortex can result from a number of causes. In relation to this, which one of the following statements is NOT correct?


  In hypercortisolism, hyperglycaemia results from increased gluconeogenesis.

  Certain types of lung cancer secrete an ACTH-like peptide that can stimulate the adrenal glands.

  The typical electrolyte disturbance in Cushing’s syndrome is a low serum sodium and a high serum potassium.

  Measurement of 24-hour free cortisol is one of the best screening investigations when Cushing’s disease is suspected.

  Lack of suppression of serum cortisol in the high-dose dexamethasone suppression test is consistent with an adrenal tumour.


Cushing's syndrome typically results in salt retention due to mineralocorticoid-like activity. This is one of the mechanisms behind Cushing's-related hypertension.