Reproductive Endocrinology Flashcards
Describe the pathway of Gas signaling
Traditional PKA pathway
Describe the Gaq signaling pathway
Phospholipase C;
PIP2 → IP3 + DAG
IP3 → ER → Increase [Ca2+]i
DAG → Activate PKC
Which Peptide hormones use the Gas / PKA pathway?
(12 total; 4 of interest)
- Corticotropin-releasing Hormone (CRH)
- Follicle-Stimulating Hormone (FSH)
- Human chorionic Gonadotropin (hCG)
- Luteinizing Hormone (LH)
Additional;
- Glucagon
- Calcitonin
- Thyroid-Stimulating Hormone (TSH)
- Parathyroid Hormone (PTH)
- Secretin
- Angiotensin II (Epithelial cells)
- Catecholamines (B-Receptors)
- Vasopressin (V2 receptor, epithelial cells)
Which peptide hormones use the Gaq signaling pathway?
(7 total; 2 of interest)
- Oxytocin
- Gonadotropin-releasing Hormone (GnRH)
Additional;
- Thyroid-Releasing Hormone (TRH)
- Growth hormone-releasing factor (GHRF)
- Angiotensin II (Vascular smooth muscle)
- Catecholamines (a-receptor)
- Vasopressin (V1 receptor, vascular smooth muscle)
What are the (4) secondary messengers identified for specific hormones?
- Cyclic AMP (cAMP)
- Cyclic GMP (cGMP)
- Calcium
- IP3 & DAG
Which Hormones use IP3 & DAG signaling?
Luteinizing Hormone-Releasing Hormone (LHRH)
Angiotensin II
Which hormones use calcium signaling?
Gonadotropin-releasing Hormone (GnRH)*
Antidiuretic Hromone (ADH)
Angiotensin II
Which hormones use cAMP signaling?
- LH*
- hCG*
- FSH*
- ACTH
- TSH
- ADH
- TRH
- PTH
- Glucagon
Within the ovaries, FSH primarily acts on which cell type? What enzyme does it stimulate directly?
FSH stimulates Aromatase activity within the Granulosa cells
*Aromatase is absent in Theca cells
Within the ovaries, LH acts primarily on which cell type?
What enzyme does it stimulate?
During which phase does LH act on the other cell type?
LH acts primarily on Theca cells and stimulates Cholesterol Desmolase activity.
LH also acts on Granulosa cells during Luteal phase
Describe the pathway of Estradiol synthesis from cholesterol
[Cholesterol Desmolase]
Chol → Pregnenolone
[3B-HSD]
Pregnenolone → Progesterone
[17a-Hydroxylase]
Progesterone → 17a-OH Progesterone
[17,20-Lyase]
17a-OH Progesterone → Androstenedione
[17B-HSD]
Androstenedione → Testosterone
[Aromatase]
Testosterone → Estradiol
Which enzymes are absent in Granulosa cells that are present in Theca cells?
Which steroid precursor must diffuse to the Theca cell and what is returned?
Granulosa cells lack 17a-Hydroxylase & 17,20-Lyase; therefore Progesterone diffuses to the Theca cells and Androstenedione is returned.
Which enzymes are present in Granulosa cells and not in Theca Cells?
Which reaction are Theca cells incapable of accomplishing because of this?
Aromatase activity is absent in Theca cells thus Testosterone cannot be converted to Estradiol.
What attribute leads to a follicle becoming the “Dominant Follicle”?
What does this result in?
The follicle with the Highest Number of FSH receptors becomes the dominant follicle. This results in an asymmetrical secretion of estradiol between ovaries.
Estradiol & Inhibin secretion from the dominant follicle have what effect on the other follicles?
Atresia of the other follicles
Identify the extrinsic factors influencing GnRH release
- Age & Health
- Environment
- Stress
How does Anorexia affect GnRH release?
Anorexia leads to decreased adipose tissue and thus decreased Leptin levels.
The decrease in Leptin leads to a decrease in GnRH release
Describe how stress influences GnRH
What other Neurotransmitter reduces GnRH release
Stress leads to an increase in CRH
→ Both Stress & CRH increase B-Endorphins
→ B-Endorphins reduce GnRH release
Dopamine also reduces GnRH release
Which pathway increases GnRH release?
a1 Adrenergic
Describe how the GnRH Pulse is produced via KNDy neurons
Neurokinin B (NKB) stimulates secretion of both;
- Kisseptin
- Dynorphin
Kisseptin stimulates GnRH release;
→GnRH Stimulates additional NKB release (Postive feedback)
Over time, Dynorphin levels increase and eventually suppresses Kisseptin and GnRH release.
These reciprocal effects result in episodic activation of KNDy neurons
Describe the relation the Inhibin & Activin relation.
How does Follistatin contribute?
Inhibin inhibits FSH secretion, while Activin stimulates it.
Follistatin binds to and suppresses Activin, thereby suppressing the stimulation of FSH secretion.
Inhibin, Activin, and Follistatin are released from which single cell type?
*Additional cells/systems produce these separately as well
Granulosa Cells
During the Luteal Phase, which (2) Gonad Peptide Hormone levels increase?
Inhibin A & Activin
During the Follicular Phase, which Gonad Peptide Hormone level increases?
Inhibin B
