CSGD Quiz 4 2004

1

Which one of the following human hormones is not a glyco-protein consisting of both alpha- and beta- subunits?


  Follicle-stimulating hormone (FSH).

  Luteinizing hormone (LH).

  Thyroid stimulating hormone (TSH).

  Prolactin (PRL).

  Chorionic gonadotrophin (HCG).


Prolactin is the only one of the hormones listed which is not a glycoprotein. It is a protein, which does not have sub-units. The correct answer is therefore D.

2

Which one of the following statements about the effect of hypothalamic hormones on pituitary hormone secretion is not correct?


  GnRH pulses result in the release of pulses of FSH and LH by the pituitary.

  CRF results in the release of ACTH by the pituitary.

  Dopamine inhibits the release of prolactin by the pituitary.

  TRH releases the pituitary from secreting TSH.

  GHRH results in the release of GH by the pituitary.


All of the statements are correct except D. TRH results in the pituitary release of TSH, not its inhibition.

3

A 23 year-old pregnant woman is involved in a motor vehicle accident and sustains a fracture of the base of the skull, which has resulted in the pituitary stalk being divided. No other damage has been sustained and the hypothalamic-hypophyseal blood vessels are not affected. Which one of the following is most likely?


  She will be shown to have no growth hormone response to insulin induced hypoglycaemia.

  Her plasma cortisol level will be low.

  Her prolactin level will be increased to levels higher than those normally seen in pregnancy.

  She will not labour unless given an infusion of oxytocin.

  She will be thirsty and her urine output will be in excess of 5 litres per day.


The division of the pituitary stalk does not affect anterior pituitary function, providing the portal vessels are intact. The production of ADH is affected, so the correct answer is E. Labour can still occur even if oxytocin production and release is affected

4

Which one of the following events is not stimulated by TSH?


  Coupling of two di-iodotyrosines (DITs) to form thyroxine.

  Iodide uptake by the thyroid via an active transport process.

  Activity of the deiodinase enzymes.

  Binding of triiodothyronine to its receptor.

  Growth of the thyroid follicle cell.


The only event not stimulated by TSH is D.

5

Iodine deficiency has been shown to be associated with all of the following effects, except


  Goitre

  Hypothyroidism

  Fetal congenital abnormalities

  Mental retardation.

  Exophthalmos.


Iodine deficiency does not result in exophthalmos, a feature seen in some patients with Grave’s disease, but does result in A, B, C,and D. The correct answer is therefore E.

6

When measuring the level of a particular hormone in the blood using an immunoassay, all of the following are usually required except


  Known amounts of the hormone to be measured to set up a “standard curve”.

  Minute amounts of a purified form of the hormone appropriately “labelled” with a radio- isotope or other label.

  Antibody to that hormone.

  A detection method to measure the total amount of “label”.

  A blood sample with an unknown amount of the hormone to be measured.


Option D is the correct answer as this is clearly wrong . It is not the total amount of “label” which is important and measured, but the amount of “bound” label. The amount of “bound” hormone to the antibody is influenced by the amount of unlabelled hormone also used in the assay. Using known amounts of unlabelled hormone allows a standard curve to be established using the “bound label” measured, and the amount of hormone in the unknown sample can then be calculated from its own“bound label” measurement.

7

Six weeks after thyroid surgery a patient is noticed to have a hoarse voice. Damage to which one of the following nerves at the time of the surgery is most likely to be the cause of this symptom?


  The superior laryngeal nerve

  The internal laryngeal nerve

  The external laryngeal nerve

  The recurrent laryngeal nerve

  The vagus nerve


The only correct answer is D.

8

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.


This boy has congenital adrenal hyperplasia, not of the salt losing type. The correct answer is therefore D. His bone age will be advanced.
Alternate:
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).

9

Which one of the following statements about the hormone adrenaline is correct?


  It acts on cytosolic receptors to increase gene expression.

  It acts on nuclear receptors to decrease gene expression.

  It acts on cell surface receptors that have intrinsic tyrosine kinase activity.

  It acts on cell surface receptors that couple to G proteins.

  It acts on a cell surface receptor with intrinsic guanylate cyclase activity.


A is incorrect: This is a feature of steroid hormones. B is incorrect: Adrenaline acts via cell surface adrenergic receptors. C is incorrect. D is correct: Adrenergic receptors are G protein-coupled receptors. E is incorrect.

10

Which one of the following is not a site of testosterone production?


  the ovary

  the fetal testis

  the adrenal medulla

  the ageing testis

  the neonate


The only site where testosterone is not produced, of the options given, is C (The adrenal medulla produces catecholamines)