Adrenal & Steroid Biochemistry Flashcards
Which class of steroid hormone is synthesized in, but not usually secreted from, the adrenal cortex?
A. Progestins
B. Glucocorticoids
C. Mineralocorticoids
D. Androgens
E. Estrogens
A. Progestins
- Progestins: from the adrenal cortex formed during menstrual cycle (corpus luteum) and pregnancy (placenta). Most important: Progesterone.
- Glucocorticoids: “Stress hormones” from the adrenal cortex that regulate major metabolic pathways. Most important: Cortisol.
- Mineralocorticoids: Regulators of renal sodium and potassium excretion, from adrenal cortex. Most important: Aldosterone.
- Androgens: The virilizing hormones from the testis, also formed in the adrenal cortex. Most important: Testosterone.
- Estrogens: Regulators of female reproductive function, from ovary and placenta. Most important: Estradiol.
Which of the following hormones are synthesized within cells of the zona glomerulosa? (name all that apply)
A. Aldosterone
B. Cortisol
C. Corticosterone
D. Dehydroepiandrosterone
E. Androstenedione
Zona Glomerulosa
A. Aldosterone
C. Corticosterone
Zona Fasciculata
B. Cortisol (and 11-deoxycortisol)
Zona Reticularis
D. Dehydroepiandrosterone
E. Androstenedione
Which adrenal hormone is the substrate for aldosterone synthase (P450 c11AS, 18- hydroxysteroid dehydrogenase)?
A. Pregnenolone
B. 11-deoxycortisol
C. Progesterone
D. Corticosterone
E. Cortisol
D. Corticosterone
P450 c11AS = Aldosterone Synthase
Cortiscosterone + P450 c11AS, 18- hydroxysteroid dehydrogenase = ALDOSTERONE
note: 11-deoxycortisol = inactive form of cortisol
What is the rate-limiting protein for adrenal steroid synthesis?
A. 11-beta hydroxylase (11-hydroxylase)
B. 21-beta hydroxylase (21-hydroxylase)
C. 17-20 lyase
D. StAR
E. Cholesterol desmolase
D. StAR
Rate-limiting enzyme: Cholesterol desmolase/P450 scc
Which of the following proteins are common to both mineralocorticoid and glucocorticoid synthesis?
A. 17-alpha hydroxylase
B. 21-hydroxylase
C. 11-hydroxylase
D. Aromatase
E. 5-alpha-reductase
B. 21-hydroxylase
C. 11-hydroxylase
What is the most important function of aromatase?
A. Testicular conversion of adrenal androgens to testosterone
B. Adrenal conversion of DHEA into androstenedione
C. Ovarian conversion of testosterone into estradiol
D. Testicular conversion of testosterone into dihydrotestosterone
E. Ovarian conversion of DHEA into testosterone
C. Ovarian conversion of testosterone into estradiol
A. Testicular conversion of adrenal androgens to testosterone - 5a-reductase
An 8-year-old boy presents to his pediatrician with a chief complaint of fatigue and constant thirst. His blood pressure is low (60/40 mmHg). On physical examination his skin is more pigmented than it was the year before though it is the middle of winter, and he shows signs of dehydration. Laboratory tests are ordered. What are the most likely levels of plasma cortisol, angiotensin II, and aldosterone in this patient?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6
E. 5
A 45-year-old male presents to his physician for a health maintenance examination. He has been treated with high doses of a steroid for a chronic inflammatory condition for several months, and the physician and patient agree to continue this regimen. The patient has blood drawn for laboratory tests. Which of the following hormones would be most likely to be undetectable in this patient’s sample? Hint: multiple choices
A. ACTH
B. Cortisol
C. Testosterone
D. Aldosterone
E. DHEA
A. ACTH
D. Aldosterone
E. DHEA
In certain target tissues, cortisol is converted into less-potent corticosterone prior to hormone-receptor complexing. What enzyme is used for this purpose?
A. Cholesterol desmolase
B. 17-20 lyase
C. 11-hydroxysteroid dehydrogenase
D. 17-alpha hydroxylase
E. 11-hydroxylase
C. 11-hydroxysteroid dehydrogenase
A newborn girl has an enlarged clitoris and nearly-fused labia. It is determined to be a congenital disease of steroid biosynthesis. What class of steroid hormone is most likely being oversecreted in this patient?
A. Progestins
B. Mineralocorticoids
C. Glucocorticoids
D. Androgens
E. Estrogens
D. Androgens
11-Hydroxylase Deficiency
Kind of Congenital Adrenal Hyperplasia:
Excess Adrenal Androgens→
↑ deoxycorticosterone (usually inactibe BUT not maintains blood volume)
↑ mineralocorticoid function
- Virilization
- Hypokalemia
- Edema & hypertension
21-Hydroxylase Deficiency
Kind of Congenital Adrenal Hyperplasia:
↑ androgen levels
↓ glucocorticoid and mineralocorticoid levels
In the neonate, this can become a life-threatening condition if blood volume and composition cannot be adequately maintained in the first few days after birth.
Dx & Rx of Congenital Adrenal Hyperplasia
*Know differences between two types*
Congenital Adrenal Hyperplasia
- Deficiency of 21-hydroxylase or 11-hydroxylase
- Reduced corticosteroids
- Elevated ACTH
- Overproduction of adrenal androgens
Diagnosis of Congenital Adrenal Hyperplasia
- Intersex phenotype of genotypic females
- Precocious puberty in males
- Adrenal glands enlarged at birth
- Elevated 17-OH-progesterone and 17-ketosteroids
- Elevated ACTH
- Electrolyte abnormalities
- Salt craving in 21-hydroxylase deficiency
Treatment of Congenital Adrenal Hyperplasia
Cortisol, even prenatally after prenatal diagnosis
5α-Reductase Deficiency
- enzyme necessary for external genetalia differenciation = inability to convert testerosterone to DHT → ambiguous external genetalia
- adrenal glands ok
- BUT other 2ry sex characteristics ok
11-hydroxysteroid dehydrogenase + inhibitor
prevents cortisol from acting on H20 balance
licorice inhibits in kidneys → ↑ H20 & Na+ retention in blood → licorice-induced hypertension
The Hypothalamo-Pituitary-Adrenal Axis
The normal feedback of this and almost all other hypothalamo-pituitary-peripheral gland axes is dominated by the product of the peripheral gland. In the example shown, cortisol dominates the feedback process. In the gonads, it would be primarily testosterone and estrogen, the sex steroids, that would feed back upon their own production. Similarly, the thyroid gland would secrete thyroid hormone, which would feed back upon the hypothalamus’ action in a long loop.
