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Medical Biochemistry > Steroids > Flashcards

Steroids Flashcards

•Name the five classes of steroid hormones (glucocorticoids, mineralocorticoids, androgens, estrogens and progestins) •Discuss steroid hormone synthesis related to STAR and desmolase (CYP11A) •Describe the steroid hormones synthesized and released from the adrenal cortex (specified for zona fasciculata, z. glomerulosa and z. reticularis) •Indicate the synthesis and the metabolic actions of cortisol •Indicate the synthesis and the metabolic actions of aldosterone •Indicate the sy

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USMLE® Step 1 flashcards
1
Q

<p>What are the 5 classes of steroid hormones?</p>

A

<p>-Glucocorticoids
-Mineralocorticoids
-Androgens
-Estrogens
-Progestins</p>

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2
Q

<p>Synthesis and secretion of cortisol and aldosterone occur in what?</p>

A

<p>Adrenal cortex</p>

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3
Q

<p>Synthesis and secretion of estrogens and progestins occur in what?</p>

A

<p>Ovaries and ovarian corpus luteum</p>

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4
Q

<p>Synthesis and secretion of testosterone occurs in what?</p>

A

<p>Testes</p>

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5
Q

<p>What is the blood carrier protein used by cortisol?</p>

A

<p>Transcortin</p>

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6
Q

<p>What is the blood carrier protein used by the sex hormones?</p>

A

<p>Sex hormone-binding protein</p>

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7
Q

<p>Hydrophobic steroid hormones can be non-specifically carried by what?</p>

A

<p>Albumin</p>

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8
Q

<p>What molecule is used to transport cholesterol into the mitochondria?</p>

A

<p>StAR (Steroidogenic acute regulatory protein)</p>

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9
Q

<p>What is the regulatory step of cortisol synthesis?</p>

A

<p>Transport of cholesterol into mitochondria by StAR</p>

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10
Q

<p>In the initial reaction of steroid hormone synthesis, cholesterol gets converted to what?</p>

A

<p>Pregnenolone</p>

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11
Q

<p>What is the role of 3-B-hydroxysteroid dehydrogenase?</p>

A

<p>Oxidizes and isomerizes pregnenolone to progesterone</p>

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12
Q

<p>What is the role of Cholesterol Esterase?</p>

A

<p>Cleaves Cholesterol esters into Cholesterol.
(this enzyme is activated by PKA)</p>

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13
Q

<p>The rate-limiting step of steroid hormone synthesis requires what two molecules?</p>

A

<p>-NADPH
-O2</p>

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14
Q

<p>What is the rate limiting enzyme in steroid hormone synthesis?</p>

A

<p>Desmolase
(aka: Cholesterol Side Chain Cleavage Enzyme CYP 11A1 P450 scc)</p>

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15
Q

<p>\_\_\_\_\_\_\_\_\_\_\_\_ reactions modify progesterone to other steroid hormones</p>

A

<p>Hydroxylation</p>

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16
Q

<p>Most enzyme (hydroxylases) in steroid biosynthesis are \_\_\_\_\_\_\_\_\_\_\_\_\_ enzymes</p>

A

<p>Cytochrome P450-dependent</p>

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17
Q

<p>What region of the Adrenal gland releases Aldosterone?</p>

A

<p>Z. Glomerulosa</p>

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18
Q

<p>What region of the Adrenal Gland releases Cortisol?</p>

A

<p>Z. Fasciculata</p>

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19
Q

<p>What region of the Adrenal gland releases androgens (DHEA, Androstenedione)</p>

A

<p>Z. Reticularis</p>

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20
Q

<p>What does ACTH stand for?</p>

A

<p>Adrenocorticotropic hormone</p>

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21
Q

<p>ACTH, through actions of cAMP, stimulate synthesis of what steroid?</p>

A

<p>Cortisol</p>

22
Q

<p>Angiotensin II/III, through actions of PIP2/IP3/Ca2+, stimulate synthesis of what steroid?</p>

A

<p>Aldosterone</p>

23
Q

<p>Follicle Stimulating Hormone (FSH), through action of cAMP, stimulates synthesis of what steroid?</p>

A

<p>Estradiol</p>

24
Q

<p>Luteinizing Hormone (LH), through action of cAMP, stimulates synthesis of what steroid?</p>

A

<p>Progesterone and Testosterone</p>

25
Q

<p>In general, what are the actions of cortisol once released?</p>

A

<p>-Stimulate gluconeogenesis
-Anti-inflammatory action
-Protein breakdown in muscle. </p>

26
Q

<p>How does cortisol counteract the action of insulin?</p>

A

<p>Cortisol leads in general to degradation of muscle protein</p>

27
Q

<p>What are the 3 ways cortisol is involved in reducing inflammation?</p>

A

<p>- Inhibits Phospolipase A2
-Less arachidonic acid available for synthesis of eicosanoids (inflammatory mediators)
-Inhibits induction of COX-2</p>

28
Q

<p>What is the role of aldosterone?</p>

A

<p>-Raises blood pressure and fluid volume
-Increases Na+ uptake</p>

29
Q

<p>What are the two main androgens?</p>

A

<p>Dehydroepiandrosterone (DHEA)
Androstenedione</p>

30
Q

<p>What type of cells contain LH receptors, which increases cAMP and PKA resulting in testosterone synthesis?</p>

A

<p>Leydig Cells</p>

31
Q

<p>What is produced by Sertoli Cells?</p>

A

<p>Dihydrotestosterone (DHT)</p>

32
Q

<p>Regarding steroid receptor mechanism of signal transduction, what are HREs?</p>

A

<p>-Hormone response elements.
-Upon binding by Receptor Protein (Rec) activated by hormone, HREs regulate transcription of adjacent genes, increasing or decreasing rate of mRNA formation.</p>

33
Q

<p>What causes Congenital Adrenal Hyperplasias? (CAH)</p>

A

<p>Deficiency of:
- 3-B-hydroxysteroid dehydrogenase
- 17-alpha-Hydroxylase</p>

34
Q

<p>What does 3-B-hydroxysteroid dehydrogenase deficiency result in?</p>

A

<p>-Vitrually no glucocorticoids, mineralocorticoids, active androgens, or estrogens</p>

35
Q

<p>What does 17-alpha-Hydroxylase deficiency result in?</p>

A

<p>Virtually no sex hormones or cortisol are produced</p>

36
Q

<p>17-alpha-Hydroxylase is abbreviated as</p>

A

<p>CYP17</p>

37
Q

<p>Mineralocorticoids and glucocorticoids are virtually absent from deficiency of what?</p>

A

<p>Classic form of
21-alpha-Hydroxylase deficiency</p>

38
Q

<p>Mineralocorticoids and glucocorticoids are deficient from deficiency of what?</p>

A

<p>Non-classic form of
21-alpha-Hydroxylase deficiency

(Note: classic form stems from almost complete absence of enzyme)</p>

39
Q

<p>What is the most common form of Congenital Adrenal Hyperplasia?</p>

A

<p>21-alpha-Hydroxylase deficiency</p>

40
Q

<p>Overproduction of Androgens leads to masculinization of external genitalia in females and early virilization in males results from deficiency of what enzyme?</p>

A

<p>21-alpha-Hydroxylase deficiency</p>

41
Q

<p>Decrease in serum cortisol, aldosterone, and coticosterone results from deficiency of what enzyme?</p>

A

<p>11-B-Hydroxylase deficiency</p>

42
Q

<p>How does 11-B-Hydroxylase deficiency cause low-renin hypertension?</p>

A

<p>Increases production of deoxycorticosterone, causing fluid retention . This hormone supresses fluid retention.</p>

43
Q

<p>Deficiency of what two enzymes leads to masculinization and virilization?</p>

A

<p>11-B-hydroxylase
21-alpha-hydroxylase</p>

44
Q

<p>What syndrome describes the results of hypercortisolism?</p>

A

<p>Cushings Syndrome</p>

45
Q

<p>Cushings syndrome is due to what?</p>

A

<p>High cortisol concentration and low ACTH concentration in plasma (high cortisol in urine)</p>

46
Q

<p>Glucocorticoid excess, as seen in Cushing's syndrome, leads to...</p>

A

<p>Protein loss
characteristic fat distribution</p>

47
Q

<p>What is Addison's disease?</p>

A

<p>Primary adrenal cortical insufficiency</p>

48
Q

<p>Addison's disease is caused by?</p>

A

<p>-Adrenal cortex atrophy due to diease
-Mostly by autoimmune destruction</p>

49
Q

<p>Addison's disease is characterized by?</p>

A

<p>Low Aldosterone and cortisol levels
High ACTH</p>

50
Q

<p>
Draw out the synthesis of steroid hormones</p>

<p>
(Memorize this diagram!!!)</p>

A

<p>
<img></img></p>

Medical Biochemistry (35 decks)

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