CSGD Quiz 4 2005

1

Which ONE of the following hormones does not interact with a cell surface receptor?


  Insulin.

  Cortisol.

  Adrenaline.

  Glucagon.

  Adreno-corticotrophic hormone.


Cortisol is a steroid hormone and therefore passes through the cell membrane to bind to cytosolic receptors.

2

Which ONE of the following statements is NOT CORRECT?


  Adrenaline is synthesized by the enzymatic modification of tyrosine in adrenal chromaffin cells.

  Testosterone is synthesized by the action of mitochondrial and microsomal cytochrome P450 enzymes acting on cholesterol in the testis.

  Thyroxine is synthesized by the iodination of tyrosine residues in thyroglobulin and released by proteolysis by the thyroid follicular cells.

  ACTH is synthesized by enzymatic processing of a pre-pro-hormone precursor synthesized on ribosomes in the adrenal cortical zona glomerulosa cells.

  Melatonin is synthesized by the enzymatic modification of tryptophan in the pineal gland.


ACTH is synthesised in the anterior pituitary.

3

In regard to the hormones FSH, LH, TSH and hCG, which ONE of the following statements is NOT CORRECT?


  They are all glycoproteins.

  They each consist of alpha- and beta- subunits.

  The alpha subunits, where they are present, are all identical.

  The beta-subunits of FSH, LH and TSH are all different.

  The beta-subunits of hCG and LH are the same.


The β-subunits of all these glycoproteins are different, which is what confers their binding specificity.

4

Which ONE of the following problems is NOT associated with acromegaly?


  Enlargement of soft tissues.

  Hypotension.

  Diabetes mellitus.

  Increased colonic polyps.

  Separation of the teeth.


Acromegaly is associated with hypertension.

5

Which ONE of the following statements about breast development is CORRECT?


  Progesterone stimulates mammary duct development during pregnancy.

  The rising prolactin concentrations at puberty are the reason for the commencement of breast development seen at that time.

  During pregnancy the high progesterone levels block the action of the rising prolactin levels on the breast.

  During pregnancy the sensitivity of the breast myoepithelial cells to oxytocin decreases.

  The mammary alveoli in the non-pregnant state are secretory.


A is incorrect: Oxytocin and prolactin are the hormones that stimulate breast development during pregnancy. B is incorrect: Pubertal breast growth is mediated by the balance of oestrogen and prolactin. C is correct: Progesterone and oestrogen both act to prevent lactation. D is incorrect: Myoepithelial sensitivity mostly regulated by oxytocin. E is incorrect: Alveoli are usually non-secretory in the non-pregnant state, except during post-partum breast feeding.

6

Which ONE of the following statements regarding lactation is CORRECT?


  Lactation is stimulated by a neuroendocrine reflex.

  Initiation of lactation requires only a decrease in progesterone levels.

  Milk production is the only requirement for successful lactation.

  Oxytocin stimulates milk production from the myoepithelial cells

  Both oxytocin and prolactin are released from the anterior pituitary.


A is correct: Mechanoreceptors in nipples --> hypothalamus --> posterior pituitary (oxytocin) + anterior pituitiary (prolactin) release --> milk ejection and production respectively B is incorrect: A decrease in oestrogen is also required. C is incorrect: Milk ejection is also required. D is incorrect: Prolactin stimulates milk production from the alveolar cells. Oxytocin promotes ejection via myoepithelial cells. E is incorrect: Oxytocin is released from the posterior pituitary.

7

Which ONE of the following statements about thyroid hormones is NOT CORRECT?


  T4 is the principal secretory product of the thyroid gland.

  T3, which is produced by the thyroid gland, is also produced by de-iodination of T4 in many tissues.

  Thyroxine binding globulin (TBG) binds 75% of circulating T4.

  T4 and T3 are also bound to transthyretin and albumin.

  T4 is more active biologically than T3.


T3 is more biologically active than T4.

8

Hypothyroidism can be due to all of the following mechanisms EXCEPT:


  Insufficient functioning thyroid parenchyma due to inflammatory destruction.

  Insufficient functioning thyroid parenchyma following the administration of radioactive iodine.

  Pharmacological treatment with lithium.

  Increased TSH synthesis by the pituitary.

  Autoimmune antibody blockade of TSH receptors.


Increased TSH synthesis would stimulate thyroid activity. Lithium interferes with thyroid hormone synthesis.

9

A 25 year-old woman with a past history of primary hypothyroidism sees her family doctor with a complaint of feeling increasingly fatigued, anorexic and nauseated over a period of 4 months. She also experiences dizziness, and her blood pressure is noted to fall by 10 mm of Hg when she stands up. Even though it is winter time, she has retained her suntan. She is underweight having lost 6 kg and looks unwell. Her menses have also become infrequent. Which ONE of the following statements about her is CORRECT?


  The weakness is most likely due to hypokalaemia (low serum potassium).

  There is a significant chance she could have adrenoleukodystrophy.

  The hormone responsible for her increased skin pigmentation is ACTH.

  Her blood pressure fall on standing is a phenomenon seen in normal women.

  She is likely to have a strong aversion to anything tasting salty.


The patient most likely has Addison's disease, meaning: A is incorrect: Addison's is salt-wasting and potassium-retaining. B is incorrect: Adrenoleukodystrophy is X-linked, and therefore only affects males. C is correct: ACTH will be raised as the pituitary attempts to counteract the hypocortisolic state. ACTH stimulates melanocytes causing skin pigmentation. D is incorrect: Blood pressure should rise slightly on standing. C is incorrect: The salt-wasting resulting from Addison's often results in salt cravings.

10

A 2-year old boy presents with early pubic hair development, an enlarged penis, tall stature and over- developed muscles for his age. His testes are of normal size for a boy of two. His older sister was born with ambiguous genitalia. Which ONE of the following statements about this boy is CORRECT?


  He has central (true) precocious puberty.

  An androgen-secreting adrenal tumour is likely in this case.

  He has the severe salt-wasting form of 21-hydroxylase deficiency.

  He should be treated with hydrocortisone for life.

  His bone age will be delayed.


A is incorrect: His precocious puberty is secondary to an excess of adrenal androgens (CAH) B is incorrect: CAH is more likely at this age. C is incorrect: The salt-wasting form usually results in a salt-wasting crises very soon after birth (e.g. 1-3 weeks). D is correct: CAH results in hypocortisolism that requires treatment. E is incorrect: His bone age is likely to be increased (growth and epiphyseal fusion will occur earlier).