Steroid hormone synthesis

Question 1

What does desmolase catalyze?

Answer 1

Cholesterol into prenenolone (precursor for all steroid hormones).

Question 2

What stimulates conversion of cholesterol into prenenolone?

Answer 2

ACTH produced by the anterior pituitary gland.

Question 3

What does 3-beta hydroxysteroid dehydrogenase catalyze?

Answer 3

The conversion of prenenolone into progesterone, as well as the parallel pathways in the glucocorticoid and androgen pathways.

Question 4

What parallel pathways does 3-beta hydroxysteroid dehydrogenase catalyze?

Answer 4

17-OH prenenolone into 17-OH progesterone (glucocorticoid) and DHEA into Androstenedione (androgen).

Question 5

What does 17-alpha hydroxylase catalyze?

Answer 5

Converts prenenolone and progesterone into their 17-OH counterparts in the glucocorticoid pathway (17-OH prenenolone and 17-OH progesterone respectively).

Question 6

What does 21 hydroxylase catalyze?

Answer 6

Converts progesterone into 11-deoxycorticosterone (mineralocorticoid) and 17-OH progesterone into 11-deoxycortisol (glucocorticoid).

Question 7

What do the 11-beta hydroxylases catalyze?

Answer 7

Catalyze the final steps in glucocorticoid and mineralocorticoid synthesis respectively.

Question 8

What does the CYP11beta form of 11-beta hydroxylase catalyze?

Answer 8

Converts 11-deoxycortisol into cortisol.

Question 9

What does the CYP11AS form of 11-beta hydroxylase catalyze?

Answer 9

Converts 11-deoxycorticosterone into corticosterone (then converted into aldosterone by 18-hydroxylase).

Question 10

What is congenital adrenal hyperplasia (CAH)?

Answer 10

It is a condition caused by deficiencies in adrenal steroid synthesis. They all present with decreased cortisol production.

Question 11

What does decreased cortisol production in CAH cause?

Answer 11

Without cortisol, the negative feedback on the pituitary is limited, leading to increased ACTH production. This eventually leads to hyperplasia of the adrenal glands.

Question 12

What are the enzymes whose deficiencies can cause CAH?

Answer 12

• 21 hydroxylase
• 11-beta hydroxylases
• 17-alpha hydroxylase

Question 13

What does 17-alpha hydroxylase deficiency present with?

Answer 13

Increased mineralcorticoids, decreased cortisol, decreased sex hormones, and increased BP.

Question 14

What does 21 hydroxylase deficiency present with?

Answer 14

Decreased mineralcoticoids, decreased cortisol, increased sex hormones, decreased BP, increased renin activity, increased progesterone and 17-OH progesterone.

Question 15

What does 11-beta hydroxylases deficiency present with?

Answer 15

Decreased aldosterone, decreased cortisol, increased 11-deoxycorticosterone, increased sex hormones, increased BP, and decreased renin activity.

Question 16

What is Cushing syndrome?

Answer 16

Glucocorticoid (cortisol excess).

Question 17

What are some of the causes of Cushing syndrome?

Answer 17

Tumors that produce excess ACTH, adrenal tumors, and long term corticosteroid administration.

Question 18

What are the symptoms of Cushing syndrome?

Answer 18

Moon face, buffalo hump, high BP, thin skin, thin arms and legs, poor wound healing, stretch mark over abdomen.

Question 19

What is Addison disease?

Answer 19

Primary renal insufficiency (deficiency of both mineralocorticoids and glucocorticoids i.e. aldosterone and cortisol, ect). Caused by destruction of the adrenal cortex.

Question 20

What are some of the causes of Addison disease?

Answer 20

Hypothalamic or pituitary dysfunction, hormone receptor deficiency, or autoimmune disease.

Question 21

What are the symptoms of Addison disease?

Answer 21

Bronze pigmentation of skin, GI disturbance, weakness, weight loss, postural hypotension, hypoglycemia, low serum Na+ and high K+, low sex hormones, high ACTH, low cortisol.

Question 22

What is the treatment for Addison disease?

Answer 22

Hormone replacement therapy (glucocorticoids and aldosterone).