9. Biochemical Synthesis of Steroid Hormones

Question 1

Classify steroid hormones

Answer 1

Glucocorticoids
Mineralocorticoids
Androgens
Estrogens
Progestogens

Question 2

What are the 3 zones without the cortex?

Answer 2

Zona glomerulosa
Zona fasciculata
Zona reticularis

Question 3

What is produced in the zona glomerulosa?

Answer 3

Mineralocorticoids

Question 4

What is produced in the zona fasciculata?

Answer 4

Glucocorticoids

Question 5

What is produced in the zona reticularis?

Answer 5

Sex hormones

Question 6

What is produced in the medulla?

Answer 6

Catecholamines

Question 7

What hormones are involved in the regulation of adrenal gland hormones?

Answer 7

CRH

ACTH

Question 8

What protein controls the uptake of cholesterol into mitochondria?

Answer 8

StAR protein

Question 9

How is cholesterol converted to pregnenolone?

Answer 9

Side-chains are cleaved
Catalysed by cytochrome P450
Requires NADPH and O2

Question 10

What enzyme converts pregnenolone to progesterone?

Answer 10

3beta-OH dehydrogenase

Question 11

Which enzymes convert progesterone to cortisol?

Answer 11

17,21,11 alpha-hydroxylase

Question 12

Which enzymes convert progesterone to aldosterone?

Answer 12

21,11 alpha-hydroxylase

Aldosterone synthase

Question 13

What are the metabolic functions of glucocorticoids?

Answer 13

1. Stimulates gluconeogenesis
2. Increases glycogen in the liver
3. Acts against insulin
4. Decreases AA uptake and protein synthesis outside of the liver
5. Breaks down protein in muscle, skin, bone
6. Increased uptake of AA by liver for gluconeogenesis
7. Mobilisation of FAs
8. Stimulates lypolysis in adipose
9. Increased fat deposition on face and trunk

Question 14

What are the actions of mineralocorticoids?

Answer 14

Na+/K+ ATPase

Facilitates uptake of Na+ and H2O from tubular lumen

Question 15

What is Congenital Adrenal Hyperplasia?

Answer 15

Autosomal Recessive disorders of cortisol biosynthesis

No negative feedback to HPA axis

Question 16

What does a deficiency in 3beta-OH dehydrogenase result in?

Answer 16

No glucocorticoids, mineralocorticoids, active androgens or oestrogens
Salt excretion in urine
Female-like genitalia

Question 17

What does a deficiency in 17-a-hydroxylase result in?

Answer 17

No sex hormones or cortisol
All progesterone is converted to aldosterone
Hypertension (Na+ and water retained)
Female-like genitalia

Question 18

What does a deficiency in 21-a-hydroxylase result in?

Answer 18

Can be partial or complete absence of mineralocorticoids and glucocorticoid absence
Overproduction of androgens
Masculinisation of external genitalia in females
Early virulisation in males

Question 19

What does a deficiency in 11-B-hydroxylase result in?

Answer 19

Decreased serum cortisol, aldosterone, corticosterone
Increased production deoxy-corticosterone
Fluid retention leading to hypertension
Over-production of androgens
Masculinisation of external genitalia in females
Early virulisation in males

Question 20

What are the effects of a cortisol deficiency?

Answer 20

Poor response to stress
Hypoglycaemia
Hyperpigmentation

Question 21

What are the effects of an aldosterone deficiency?

Answer 21

Hyperkalaemia
Hyponatraemia
Disturbs cardiac rhythm
Hypotension

Question 22

What are the effects of combined cortisol and aldosterone deficiency?

Answer 22

Vascular collapse
Shock
Death
Overproduction of ACTH leading to adrenal hyperplasia

Question 23

How are CAHs treated?

Answer 23

Daily glucocorticoid and mineralocorticoid replacement

Restore volume, electrolyte and glucose imbalances