Steroid Biosynthesis Flashcards Preview

SF3-EXAM 4 (CAMELITA) > Steroid Biosynthesis > Flashcards

Flashcards in Steroid Biosynthesis Deck (32)
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1

C21 steroids

  • Progestins-progesterone, pregnenolone
  • Glucocorticoids- cortisol, corticosterone
  • Mineralorcorticoids- aldosterone, 11-deoxycorticosterone

NOTE: C21 steroids with OH at C17 are called 17- hydroxysteroids

2

C19 Steroids

Androgens-testosterone, androstenedione, DHEA, DHT

3

C18 steroids

Estrogens- Estradiol, estrone, estriol

4

Conversion of cholesterol to pregnenolone is by ____________ enzyme.

Side-chain cleavage enzyme (CYP 11A1)

NOTE: This occurs in the inner mitochondrial membrane and this step is rate-limiting for steroidogenesis.

5

Most steroidogenic enzymes belong to the ________ family and are thus reffered to as CYPs.

P-450 monooxidase gene family

6

Aldosterone is inhibited by ________.

ANP

NOTE: Aldosterone is stimulated by angiotensin II, high potassium, and acutely elvated ACTH.

7

___________ cataylzes the last 3 reactions fro 11-deoxycorticosterone (DOC) to aldosterone.

Aldosterone synthase (CYP11 B2)

*This enzyme is unique to the zona glomerulosa

8

What role does ACTH play in the transport of cholesterol?

ACTH increases the number of adrenocotical cell receptors for LDL

NOTE: ACTH also increases de novo synthesis of cholesterol from acteyl CoA (primarily catalyzed by cholesterol esterase hydroxylase a.k.a hormone sensitive lipase)

9

Which hormones is necessary for the formation of cortisol?

CYP 17 17 a-hyroxylase

10

Cortisol is reversibly inactivated to cortisone by _______.

11b-hydroxysteroid dehydrogenase Type 2

NOTE: This serves to protect mineralocorticoid receptors in aldosterone responsive cells

11

__________ converts cortison back to cortisol in tissues expressing the glucocorticoid receptor.

11b-HSD1

12

_________________ inhibits CYP11B1.

Metyrapone

13

Corticosteroids and their relative glucocorticoid and mineralocorticoid activities compared to cortisol

14

Cushing's syndrome

A constellation of clinical abnormalities caused by chronic high levels of cortisol or related corticosteroids

  • Central obesity
  • Hirsuitism
  • Hypocalcemia
  • Hyperpigmentation
  • Metabolic syndrome

15

Cushing's disease

Excess pituatary production of ACTH, generally secondary to a pituitary adenoma

16

What enzyme is unique to the zona reticularis?

17,20 lyase (CYP 17)

NOTE: The major androgen secreted by the zona reticularis is DHEA

17

________ inhibits cholesterol side-chain cleavage enzyme, 17a-hydroxylase and 17,20 lyase activity.

Ketoconazole

18

____________ deficiency accounts for 90% of all congenital adrenal hyperplasia cases.

21 B- Hydroxylase

NOTE: If there is a 21 B- hyrdroxylase deficiency 17-OH Progesterone will be elevated, which will lead to an elevation in androgen secretion. 

19

Treatment for congenital adrenal hyperplasia

  • Long-term glucocorticoid or aldosterone replacement (or both)

20

What is the major difference between congenital adrenal hyperplasia as result of 11B-hydroxylase deficiency as opposed to 21- B- hydroxylase deficiency?

Hypertension along with hypokalemia

NOTE: It should be treated with glucocorticoids

21

Testosterone synthesis from cholesterol can take four pathways, the _____ pathway is preferred.

D5

22

Human testes secrete a small portion of DHT. Most DHT is derived from peripheral conversion of testosterone by __________.

5a-reductase type 2

23

Human testes make small, but significant amounts of 17b-estradiol. Most E2 comes from peripheral _________ of androstenedione and testosteron.e

Aromatization

24

17B hydorxysteroid dehyrogenase (TYPE 3) mutation is caused by mutations in the _______ gene.

HSD17B3

*Autosomal receissive

NOTE: It is clinically indistinguishable from androgen insensitivity syndrome in prepubertal patients

25

5a- reductase deficiency

  • Genetic males are born with ambiguous genitalia
  • Clinical abnormalities range from infertility with normal male anatomy to underdeveloped male anatomy with hypospadias to predominant female genitalia

26

CYP19 is also known as __________

AROMATASE

27

Two cell model of Steroidogenesis in the dominant ovarian follicle

28

The liver convers estradiol and estrone to _______.

Estriol

NOTE: Hepatic enzymes add glucuronide or sulfate moieties for excretion in the bile

29

The major metabolite of progesterone is ___________, which is conjugated with glucuronide and excreted in urine.

Pregnanediol

30

_______________ convert cortisol to cortisone. 

Syncytiotrophoblasts

NOTE: Syncytiotrophoblasts lact CYP17