This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Female Sex Hormones – Estrogens”.
1. Which hormone controls the growth of female genital organs?
a) Estrogen
b) Progesterone
c) FSH
d) LH
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Explanation: Estrogens are hormones capable of generating some biological effects, of which the modifications in estrus of mammals are the most common. They include the development of the reproductive organs of females.
2. Which is the principal estrogenic hormone in circulation?
a) Estrone
b) β-Estradiol
c) Estriol
d) FSH
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Explanation: β-estradiol is the principal estrogenic hormone in circulation and the most active source of estrogen. This hormone and estrone are in metabolic equilibrium with each other. It is involved in the regulation of the estrous and menstrual reproductive cycles of females.
3. Which is the principal estrogenic hormone found in the urine of pregnant women?
a) Estrone
b) β-Estradiol
c) Estriol
d) FSH
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Explanation: There are certain estrogens which are naturally occurring in human beings. Among them, Estriol is the primary estrogen present in the urine and placenta of pregnant women. Estriol levels are almost undetectable in women who are not pregnant.
4. β-estradiol and estrone are interconvertible.
a) True
b) False
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Explanation: Estrone is a hormone formed in the follicles but released into the blood as β-estradiol. It is transformed into estriol in the liver. Estrone and β-estradiol are interconvertible. Estrone is an oestrogen, primarily an agonist of the ER alpha and ERβ oestrogen receptors. It is much less active than estradiol, and is a relatively weak oestrogen as such.
5. Estriol is produced from estrone.
a) True
b) False
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Explanation: Estriol is derived from estrone hydroxylation at C16 and by ketone group reduction at C17. It is the primary metabolite that is present in urine. Estriol stimulates the development of the uterus and eventually prepares the body of a woman for giving birth.
6. What is the correct order of potency of estrogenic hormones in human body?
a) β-Estradiol < estrone < estriol
b) β-Estradiol > estrone > estriol
c) Estriol > β-Estradiol > estrone
d) Estrone > estriol > β-Estradiol
View Answer
Explanation: β-Estradiol is 10 times more effective than estrone and 300 times more powerful than estriol. These hormones regulate mammary duct system development and various other phenomena. In non-pregnant women who are between the menarche and menopause phases of life, estradiol is the most significant oestrogen.
7. How are the estrogens produced in the ovary?
a) From maturing graffian follicles
b) From Secondary follicles
c) From Leydig cells
d) From Sertoli cells
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Explanation: Two classes of sex hormones, progesterone and oestrogen, are formed and released by the ovaries. In the ovary estrogens are formed by the maturing Graffian follicles. Both thecal cells and granulosa cells are involved in this process.
8. Which all pituitary gonadotropins are involved in the stimulation of estrogen secretion?
a) FSH and LH
b) LTH and LH
c) FSH, LTH and TSH
d) FSH, LH and LTH
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Explanation: All three pituitary gonadotropins namely FSH, LH and LTH are active in estrogen secretion stimulation. Estrogens are sometimes formed in limited concentrations in the adrenal cortex, placenta and testes.
9. What are the precursor molecules for the synthesis of estrogens?
a) Testosterone and Androstenedione
b) Testosterone and Progesterone
c) Androstenedione and Progesterone
d) Progesterone and Pregnenolone
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Explanation: Androgenic steroids such as testosterone and androstenedione are precursors in the testes, ovaries, adrenal cortex and placenta for the synthesis of estrogens. The transition to β-estradiol and estrone, of the natural C19 steroids requires the elimination of the angular-CH3 group at C10.
10. Which among the enzymes of estrogen synthesis require molecular oxygen and NADPH?
a) Aromatase
b) Hydroxylases
c) Dehydrogenases
d) Lyases
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Explanation: The conversion of natural steroid hormones to estrogens are carried out by various enzymes including aromatase, hydroxylases (mono-oxygenases) and dehydrogenases. Among them, hydroxylases require molecular oxygen and NADPH for its activity.
11. Which cells convert cholesterol to pregnenolone in the pathway for the synthesis of estrogens?
a) Acinar cells
b) Follicular cells
c) Steroidogenic cells
d) C cells
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Explanation: Cholesterol is transformed by steroidogenic ovarian cells to pregnenolone and progesterone, identical to the process functioning in the adrenal cortex. A certain level of progesterone is also produced by luteal cells.
12. Which enzyme converts testosterone to beta-estradiol in the pathway for the synthesis of estrogens?
a) Aromatase
b) Hydroxylases
c) Dehydrogenases
d) Lyases
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Explanation: Testosterone is converted into β-estradiol in granulosa follicle cells, catalyzed by the microsomal enzyme aromatase, which results in the aromatization of ring A. The enzyme is mono-oxygenase, which includes Cyt. P450 that needs both NADPH and molecular O2.
13. Theca interna cells of graafian follicles converts both pregnenolone and progesterone into which molecules?
a) Testosterone and estrogen
b) Estrogen and FSH
c) Testosterone and Estradiol
d) Testosterone and androstenedione
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Explanation: Graafian follicle theca interna converts both pregnenolone and progesterone to testosterone and androstenedione. These are the precursor molecules for synthesizing estrogen. Androstenedione is a hormone-steroid. Androstenedione is used to increase the hormone testosterone production to boost athletic performance, construct muscle, decrease body fat, etc.
14. Which among the following estrogens can be produced in extraovarian tissues, viz. liver, muscles, adipose tissue, etc.?
a) β-Estradiol and estrone
b) β-Estradiol and Progesterone
c) Estrogen and Progesterone
d) β-Estradiol and Testosterone
View Answer
Explanation: It is possible to produce β-Estradiol and estrone in extraovarian tissues, like Muscles, liver, adipose tissue, etc. These are derived from DHEA, testosterone and androstenedione. Aromatase expression mainly accounts for the extra glandular (peripheral) formation of oestrogen and increases as a function of body weight and advancing age in adipose tissue and probably the skin.
15. Which enzyme is responsible for the interconvertibility of the estrogens, β-Estradiol and estrone?
a) Aromatase
b) 17-β-estradiol dehydrogenase
c) Reductase
d) Lyase
View Answer
Explanation: In extra-ovarian tissues such as the liver and placenta, β-estradiol and estrone are interconvertible. The unique enzyme 17-β-estradiol dehydrogenase catalyzes this process. This enzyme belongs to the oxidoreductase family, specifically those that function on the donor group CH-OH with either NAD+ or NADP+ as the accepter.
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