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GIGU and Repro > Steroid Biosynthesis > Flashcards

Steroid Biosynthesis Flashcards

1
Q

Which of the following reasons a is true in regard to why organs like the kidney, colon, and parotid glands are able to avoid sodium/water retention that would be induced by high circulating levels of glucocorticoids?

A. They do not contain an MR receptor which cortisol has a high affinity for

B. They contain the enzyme 11B-hydroxysteroid dehydrogenase which metabolizes cortisone to cortisol which has a lower affinity for MR than cortizone

C. They contain the enzyme 11B-hydroxysteroid dehydrogenase which metabolizes cortisol to cortizone which has a lower affinity for MR than cortisol

D. None of the above

A

C. They contain the enzyme 11B-hydroxysteroid dehydrogenase which metabolizes cortisol to cortizone which has a lower affinity for MR than cortisol

NOTE: Licorice inhibits 11B-hydroxisteroid dehydrogenase, which can cause hypertension due to salt retention

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2
Q

How does a burst of glucocorticoid in normal term infants prevent the development of Infant Respiratory Distress Syndrome?

A. Stimulates lungs to increase rate of breathing

B. Stimulates surfactant production

C. Has no effect on the lungs

D. None of the above

A

Stimulates surfactant production

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3
Q

Which of the following could be utilized in treating benign prostatic hyperplasia (BPH) or male patterned baldness?

A. increase in 5a-reductase

B. increasing licorice intake

C. increase in vitamin D activation via sunlight

D. administration of Finasteride

A

administration of Finasteride

  • this is an inhibitor of 5a-reductase
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4
Q

Which of the following is the rate limiting enzyme responsible for converting cholesterol to pregenolone in the adrenal cortex?

A. 5a-reductase

B. Desmolase in the cytosol

C. Desmolase in the mitochondria

D. 21a-lyase

A

Desmolase in the mitochondria

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5
Q

Which of the following directly regulates desmolase the rate limiting enzyme responsible for converting cholesterol into pregenolone?

A. Aldosterone

B. Renin

C. Sodium

D. ACTH

A

ACTH

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6
Q

What are other names that 20,22-Desmolase is known as? (2)

A

cytochrome P450 SCC

CYP11A1 (gene that encodes desmolase)

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7
Q

Desmolase is found in all steroid producing organs, which of the following are steroid producing hormones?

A. Testes

B. Adrenal gland

C. Ovary

D. Placenta

E. All of the above

F. All but C

A

All of the above

ATOP

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8
Q

What specific effect does desmolase have on cholesterol to make it become pregenolone?

A. Remove 5 carbons and a double bond

B. Remove 6 carbons and add a double bond

C. Add 6 carbons and remove a double bond

D. None of the above

A

Remove 6 carbons and add a double bond

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9
Q

Pregenolone is THE MOST important biochemical intermediate as it is used as a substrate to produce other steroid hormones. What are 5 steroid hormones pregenolone is used to produce?

A

Progesterone

Aldosterone

Cortisol

Testosterone

Estradiol

PACT-E

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10
Q

T/F: Glubulins like SHBG and CBG are responsible for transporting steroid hormones in the blood and are mostly made in the liver

A

True

CBG: 80-90% glucocorticoid hormone + progesterone

SHBG: T, DHT, estradiol

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11
Q

Which of the following acts as a vasocontrictor, stimulates thirst, and increases water retention?

A. ACTH

B. ADH/vasopressin

C. Aldosterone

D. None of the above

A

ADH/vasopressin

NOTE: Aldosterone stimulates kidneys to increase sodium and water retention

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12
Q

Which of the following is true of classical and nonclassical forms of Andrenal Hyperplasia?

A. Only classical form causes deficiencies in adrenal enzymes used to synthesize glucocorticoids

B. See a decrease in cortisol and androgen precursors in both classical and nonclassical

C. Both cause a deficiency in adrenal enzymes used to synthesize glucocorticoids

D. None of the above

A

Both cause a deficiency in adrenal enzymes used to synthesize glucocorticoids

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13
Q

What are the results or symptoms seen in patients with even mild congenital hyperplasia?

A. Life threatening sinus and pulmonary infections

B. Orthostatic syncope

C. Shortened stature

D. Severe acne

E. All of the above

A

All of the above

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14
Q

What are three common symptoms seen in female patients with Adrenal Hyperplasia?

A

Hirutism

Oligomenorrhea (light or absence in period >35 days)

Infertility

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15
Q

Loss of which of the following enzymes would directly lead to a accumulation of Progesterone and 17-hydroxyprogesterine, which are precursors of aldosterone and cortisol respectively?

A. 11B-hydroxylase

B. 17,20-lyase

C. 21a-hydroxylase

D. None of the above

A

21a-hydroxylase

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16
Q

Loss of which of the following enzymes would directly lead to a accumulation deoxycorticosterone and 11-deoxycortisol and thus decrease in aldosterone and cortisol respectively?

A. 11B-hydroxylase

B. 17,20-lyase

C. 21a-hydroxylase

D. None of the above

A

11B-hydroxylase

17
Q

Which of the following is true of primary aldosteronism?

A. Leads to excessive release of Na and H2O from the kidney

B. Leads to retention of H+ and K+

C. See a decrease in blood volume that often results in hypotension

D. Promotes excretion of H+ and K+

A

Promotes excretion of H+ and K+

18
Q

Conn Syndrome is an endocrine disorder of the adrenal glands. What 4 things, as indicated by Dr. Staudinger, would you see in Conn Syndrome?

A

Excessive aldosterone secretion

Sodium retention

Loss of potassium

Hypertension

19
Q

Which of the following steroids activate Mineralcorticoid Receptor (MR) with the highest efficacy SECOND to aldosterone?

A. Testosterone

B. Hydrocortisone (cortisol)

C. Cortisone

D. 11-deoxycorticosterone

A

11-deoxycorticosterone

NOTE: see high amounts of this in a 11B-hydroxylase deficiency (Cyp11B1)

20
Q

Which of the following steroid hormones increase Na-retention?

A. Testosterone

B. Hydrocortisone (cortisol)

C. Cortisone

D. 11-deoxycorticosterone

A

All of them

A. Testosterone

B. Hydrocortisone (cortisol)

C. Cortisone

D. 11-deoxycorticosterone

21
Q

Althourgh a deficiency in 11B-hydroxylase (Cyp11B1) causes decreased synthesis of aldosterone, whu do patients still end up with hypertension?

A

We will still see elevated levels of 11-deoxycorticosterone which has relatively high affinity for MR. MR promotes Na retention –> hypertension in PTs

22
Q

Look at this

A

Blue box will likely be a test question

23
Q

T/F: 11B-hydroxylase deficiency can lead to overproduction of androgens which causes masculinzation and virilization

A

True

24
Q

ACTH is a 39 AA structure secreted by the anterior pituitary, and is responsible for stimulating the production of what important steroid hormone?

A

Cortisol

25
Q

ACTHhas long term activation, increases lipoprotein uptake into corticol cells, increases availability of cholesterol in adrenal cortex, and stimulates transcription of genes coding for steroidegenic enzymes. Name 2 genes or enzymes it stimualtes production for/

A

CYP11A1: desmolase

CYP11B1: 11B-hydroxylase

26
Q

CYP17A1 is the same as what enzyme?

A

17,20-lyase

27
Q

Mutations in CYP17A1 is associated with 17a-hydroxylase/17,20-lyase deficiency, and what 2 resulting abnormalities?

A. oligomenorrhea and hirutism

B. hirutism and hypertension

C. pseudo hermaphroditism and adrenal hyperplasia

D. none of the above

A

pseudo hermaphroditism and adrenal hyperplasia

28
Q

Loss or deficiency in which of the following enzymes results in 46-XY DSDs while production of glucocorticoids stays intact?

A. 11B-hydroxylase

B. 17,20-lyase

C. 21a-hydroxylase

D. None of the above

A

17,20-lyase

NOTE: see increase in 17a-hydroxyprogesterone but decrease in androsternedione–> Testosterone–> estradiol and DHT

29
Q

Which of the following is found exclusively in the liver?

A. 25-hydroxycholesterol and enzyme 1a-hydroxylase

B. 1,25 dihydroxycholecalciferol and eznyme 1a-hydroxylase

C. 25-hydroxycholelciferol and enzyme 25-hydroxylase

D. Calcitriol and enzyme 25-hydroxylase

A

25-hydroxycholelciferol and enzyme 25-hydroxylase

25-hydroxycholeciferol is the precursor of 1,25-dihydroxycholecalciferol (calcitriol) which is made in the kidney via 1a-hydroxylase

30
Q

What two ways is cholecalciferol (vitamin D3) obtained for vitamin D production?

A
  1. diet: as Vitamine D2(erggocalciferol) is absorbed through intestine
  2. skin: where 7-dehydrocholesterol in the skin is converted to Vitamin D2 via UV radiation
31
Q

Which of the following signals 1a-hydroxylase in the kidney to convert 25-hydroxycholecalciterol to 1,25-dihdroxycholecalciferol (calcitriol)?

A. Calcitriol)

B. PTH and high [phosphate]

C. Cortisol and PTH

D. PTH and low [phosphate]

A

PTH and low [phosphate]

NOTE: Calcitriol inhibits 1a-hydroxylase

32
Q

T/F: Male patients with 11-hydroxylase deficiency often have normal genitalia at birth, while females have ambiguous genitalia

A

True

33
Q

A 1 year old female is found to have high blood pressure on multiple visits to your office. On examination, the patient has ambiguous genitalia. Further labratory workup reveals low serum aldosterone and high serum testosterone. Which of the following is most likely to be elevated in this patient?

A. 17-hydroxylase

B. 11B-hydroxylase

C. 21-hydroxylase

D> 5’deodinase

E. 11-deoxycorticosterone

A

11-deoxycorticosterone

NOTE: 11B-hydroxylase is likely to be deficient

34
Q
A

A. Cholecalciferol (D3)

GIGU and Repro (35 decks)

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