ELC 2 Flashcards
Which of the following is incorrect?
a) POMC, ACTH and b-lipoprotein are secreted from corticotropes in the anterior pituitary in response to CRH
b) ACTH binds melanocortin-2 receptors which are present only in the fasciculata layer
c) The adrenal medulla contains chormaffin cells that secrete epinephrine and a small amount of norepinephrine
d) the blood supply to the adrenal gland enters in the sub capsular region, closest to the zone glomerulosa.
(2.1)
b) False- melanocortin 2 receptors are found in all three layers of the adrenal cortex, but particularly in the fasciculata layer (cortisol production)
What are the layers of the adrenal gland and what are the main hormones produced?
(2.1)
cortex:
- zona glomerulosa: mineralocorticoids (aldosterone)
- zona fasciculata: (glucocorticoids (cortisol)
- zona reticularis: androgens (DHEA and androstenedione)
- medulla: epinephrine
Which of the following is false?
a) The adrenal cortex and medulla have the same origins
b) By the second postnatal month, much of the fatal adrenal cortex is lost
c) neural crest cells migrate ventrally and invade the core of fatal adrenal gland
d) fetal adrenal gland is used by fatal placenta for synthesis of oestrogen protecting the foetus from very high levels of maternal hormones.
(2.1)
F- the cortex develops from mesenchyme and the medulla from neural crest cells
Which of the following is incorrect?
a) Only the fasciculata and reticular layers can synthesise cortisol
b) aldosterone synthase converts corticosterone to aldosterone and this enzyme is only present in glomerulosa cells
c) 21a-hydroxylase deficiency would lead to inadequate production of only glucocorticoid hormones
d) 11B-HSD catalyses conversion of active cortisol to cortisone and therefore acts as a shunt to protect the mineralocorticoid receptor.
(2.1)
c) false- deficiency of 21a-hydroxylase would lead to inadequate production of both glucocorticoid and mineralocorticoid hormones. Affected infants have symptoms of “salt loss” (hypotension, dehydration) ad glucocorticoid deficiency (hypoglycaemia). There is also resultant increased synthesis of adrenal androgens and enhanced growth of the adrenal gland- classical clinical syndrome of salt-losing, virilising congenital adrenal hyperplasia.
Which of the following about the actions of cortisol is incorrect?
a) In the early fasting state, cortisol stimulates gluconeogenesis and glycogenolysis to increase blood glucose as well as protein and fat metabolism effects
b) reduces bone formation
c) potent immunosuppressive and anti-inflammatory activity
d) cortisol only acts on the principal glucose regulatory tissues- liver, fat and muscle
(2.1)
d) false- Most body tissues, including bone, skin, other viscera, hematopoietic and lymphoid tissue, and the central nervous system (CNS), are target sites for glucocorticoid action.
Which of the following about CBG is true?
a) increased CBG in high oestrogen states (pregnancy)
b) increased CBG in hyperthyroidism
c) increased CBG in diabetes
d) albumin has greater capacity to bind cortisol than CBG therefore 75% of the cortisol is bound to albumin.
(2.1)
a) true
b) decreased CBG
c) decreased
d) false, albumin has higher capacity to bind but lower affinity- 75% bound to CBG.
Which of the following is false?
a) ACTH levels exhibit only circadian rhythm and not pulsatile behaviour
b) The corticotrophins release ACTH in a circadian rhythm, greater in the early morning and less late in the afternoon and evening.
c) ACTH has a shorter half life
in plasma
(2.1)
a) false- it exhibits both pulsatile and circadian- pulsatile because the pulsatile release of CRH by hypothalamus.
Which of the following about the adrenal medulla is false?
a) adrenal medulla is essentially modified neural tissue, effectively acting like a post ganglionic neuron
b) Chromaffin cells secrete catecholamines and androgens
c) Norepinephrine has a tyrosine and dopamine precursor
d) Only chromaffin cells contain the enzyme required to synthesise epinephrine
b) false- only catecholamines
What do the following results from the dexamethasone suppression test indicate about the cause of the hypercortisolism?
1. ACTH is high and cortisol has not been suppressed
- ACTH is normal but cortisol has been suppressed
(2. 2)
- Suspect Ectopic ACTH syndrome- (or adrenal hyper secreting tumour) cortisol has not been suppressed even thought pituitary has been suppressed by dexamethasone.
- Suspect Cushing’s disease
What is the most common cause of hypercortisolism?
2.2
Iatrogenic or exogenous corticosteroid exposure s the most common cause of hypercortisolism.
What is the most common cause of endogenous Cushing’s syndrome?
(2.2)
ACTH-secreting pituitary adenomas = cushing’s disease
What is the most common type of ectopic ACTH-secreting tumour?
(2.2)
Small cell lung carcinoma.
note, in general, tumours causing the ectopic ACTH syndrome tend to secrete a disproportionately greater proportion of POMC precursors.
What is Nelson’s syndrome a complication of?
2.2
Bilateral adrenalectomy owing to Cushing’s disease- the loss of negative feedback on the pituitary resulting in excess ACTH
Which is not a clinical feature of cushing’s syndrome?
a) facial plethora
b) supraclavicular fullness
c) violaceous striae
d) increased libido
e) glucose intolerance or diabetes
(2.2)
d) false- decreased libido
Which of the following is not a clinical feature of Addison’s disease?
a) hypotension
b) hyponatraemia
c) hyper pigmentation
d) weight gain
e) loss of axillary and pubic hair and decreased libido
(2.2)
a) true due to salt loss
b) true due to aldosterone loss
c) true due to excess MSH
d) false- weight loss, anorexia is common in Addison’s disease
e) true
