Steroid Biosynthesis

Question 1

What are all steroid hormones synthesized from?

Answer 1

Cholesterol

Question 2

What enzyme controls the rate-limiting step of steroid hormone synthesis?

Answer 2

Desmolase

Question 3

Desmolase activity is regulated by?

Answer 3

ACTH

Question 4

What reaction is catalyzed by Desmolase?

Answer 4

Cholesterol –> Pregnenolone

Question 5

Pregnenolone can then go on to create what other steroid hormones?

Answer 5

Aldosterone
Cortisol
Sex hormones - testosterone, estradiol, progesterone

Question 6

Where does steroid hormone synthesis take place?

Answer 6

Adrenal cortex

Question 7

Aldosterone can bind and activate what receptor?

Answer 7

Mineralcorticoid Receptor (MR)

Question 8

Activation of the Mineralcorticoid Receptor results in what?

Answer 8

Increased Na+ retention = hypertension!

Question 9

Primary Aldosteronism/Conn’s Syndrome

Answer 9

Adrenal glands produce too much Aldosterone!

Question 10

Too much Aldosterone results in?

Answer 10

Retention of Na+
Loss of K+
Body holds on to too much water
Increased blood volume and blood pressure

Question 11

Main result of Primary Aldosteronism/Conn’s Syndrome?

Answer 11

INCREASED BLOOD PRESSURE

Question 12

Adrenal Hyperplasia

Answer 12

Deficiencies in adrenal enzymes that are used to make glucocorticoids
– This causes an increase in both cortisol PRECURSORS and androgens (sex hormones)

Question 13

What are some signs of adrenal hyperplasia?

Answer 13

Life-threatening infections
Acne, short stature
Hirsutism
Oligomenorrhea and Infertility

Question 14

Hirsutism

Answer 14

Male pattern body hair on women - seen with adrenal hyperplasia

Question 15

Oligomenorrhea

Answer 15

Infrequent or light menstrual cycles - seen with adrenal hyperplasia

Question 16

Cholesterol is converted to Pregnenolone

Pregnenolone is then converted to what 2 things?

Answer 16

Progesterone AND 17OH-progesterone

Question 17

Progesterone is converted to what?

Answer 17

11-deoxycorticosterone

Question 18

17OH-progesterone is converted to what?

Answer 18

11-deoxycortisol

Question 19

What enzyme is responsible for creating 11-deoxycorticosterone and 11-deoxycortisol?

Answer 19

21-hydroxylase

Question 20

11-deoxycorticosterone is converted to what?

Answer 20

Aldosterone

Question 21

11-deoxycortisol is converted to what?

Answer 21

Cortisol

Question 22

What enzyme is responsible for creating Aldosterone and Cortisol?

Answer 22

11beta - hydroxylase

Question 23

Adrenal hyperplasia can be seen with the loss of what enzymes?

Answer 23

21 - hydroxylase

11beta - hydroxylase

Question 24

11beta - hydroxylase deficiency

Answer 24

DECREASED aldosterone and cortisol

INCREASED 11-deoxycorticosterone and 11-deoxycortisol

Question 25

11beta - hydroxylase deficiency results in what main symptom and why?

Answer 25

HIGH BLOOD PRESSURE because 11-deoxycorticosterone also has a high affinity to bind to the same receptor as aldosterone (MR) -- Thus you have high blood pressure even without the formation of aldosterone

Question 26

What is the HPA for steroid hormones, specifically cortisol?

Answer 26

Hypothalamus - CRH Anterior pituitary - ACTH Adrenal glands - Cortisol - Cortisol has (-) feedback on both CRH and ACTH

Question 27

ACTH binds to what type of receptor in the Zona Fasciculata in the adrenal glands?

Answer 27

GPCR

Question 28

What is the intracellular pathway events after ACTH binds to a GPCR in the adrenal gland?

Answer 28

Stimulates Adenylyl Cyclase Increases cAMP Activates protein kinase A Creates cortisol

Question 29

In a tumor cell, what is always active in the ACTH mediated intracellular signaling pathway?

Answer 29

protein kinase A

Question 30

17,20 Lyase deficiency

Answer 30

Deficient production of androgens and 46XY development

Question 31

Cholecalciferol (D3) can be formed in what 2 places in the body?

Answer 31

Skin and intestines

Question 32

The skin creates D3 using?

Answer 32

7-dehydrocholesterol + UV light

Question 33

The intestines creates D3 using?

Answer 33

D2 (Ergocalciferol)

Question 34

Cholecalciferol (D3) is then transported from the skin and intestines to?

Answer 34

Liver

Question 35

The liver takes cholecalciferol (D3) to?

Answer 35

25-hydroxycholecalciferol

Question 36

The liver creates 25-Hydroxycholecalciferol using what enzyme?

Answer 36

25-hydroxylase

Question 37

25-hydroxycholecalciferol is then sent to where?

Answer 37

Kidney

Question 38

The kidney takes 25-hydroxycholecalciferol to what?

Answer 38

1,25 - dihydroxycholecalciferol = calcitriol

Question 39

The kidney uses what enzyme to create calcitriol, the active form of Vitamin D?

Answer 39

1alpha-hydroxylase

Question 40

What is the active form of Vitamin D?

Answer 40

1,25-dihydroxycholecalciferol (calcitriol)

Question 41

Where is the active form of Vitamin D synthesized?

Answer 41

Kidney