MENSTRUAL CYCLE
| A | Desmolase | |
| B | Isomerase | |
| C | Aromatase | |
| D | Hydroxylase |
| A | Desmolase | |
| B | Isomerase | |
| C | Aromatase | |
| D | Hydroxylase |
Aromatase
| A |
Lactation |
|
| B |
Ovulation |
|
| C |
Secretory endometrium |
|
| D |
Vaginal cornification index |
Which of the following enzyme is associated with the conversion of androgen to oestrogen in a growing ovarian follicle is:
| A |
Aromatase |
|
| B |
5 alpha reductase |
|
| C |
Desmolase |
|
| D |
Isomerase |
Aromatase enzyme: In a normal ovary, LH acts on the theca interstitial stromal cells, whereas FSH acts on granulosa cells. In response to LH the thecal cells secretes androgen, and the produced androsendione is converted in the granulosa cells to estrogen by the action of aromatase enzyme.
Ref: Physiology By James N. Pasley 2nd Edition, Page 145 ; Androgens in health and disease By William J. Bremne Page 84 ; Padé approximation and its applications: Diagnosis and management of PCOS, Issue 765, By Luc Wuytack, Page 107
FSH and LH both are inhibited by ‑
| A |
Cortisol |
|
| B |
Aldosterone |
|
| C |
Estrogen |
|
| D |
Progesterone |
Ans. is ‘c’ i.e., Estrogen
Consistent with the phenomenon of negative feedback in which the secretion of the target hormone inhibits its trophic hormone, pregesterone inhibits LH and inhibin inhibits FSH.
- Estrogen, whose secretion is stimulated by both LH and FSH, inhibits both LH and FSH.
- Progesterone and estrogen act at both hypothalamic and pituitary levels while inhibin secreted by granulosa cells acts only on the pituitary.
- Under certain conditions, estrogen causes stimulation (positive feedback) rather than inhibition of LH, e.g., at ovulation.
| A | Only by theca cells | |
| B |
Only by granulosa cells |
|
| C |
Both theca and granulosa cells |
|
| D |
None of the above |
Ans. is ‘c’ i.e., Both theca and granulosa cells
Ovarian follicle contains two types of cells in preovulatory phase :-
i) Granulosa cells :- Secrete mainly estrogen and very minimal amount of progesterone.
ii) Theca cells (interna & externa) Theca interna cells provide androgen and pregnenolone to granulosa cells to convert them into estrogen and progesterone respectively.
After ovulation, corpus luteum contain two types of cell :-
i) Granulosa luteal cells (formed by luteinization of granulosa cells) :- Produce mainly estrogen and minimal progesterone.
ii) Theca luteal cells (formed by luteinization of theca interna cells) :- Produce mainly progesterone.
