Follicle Stimulating Hormone & Luteinizing Hormone
What is the chemical nature of the two gonadotrophs?
Both protein hormones (LH & FSH)
What is metestrus?
Corpus luteum (CL) secreted progesteron supresses FSH and LH secretion, stimulates endometrial secretion in preparation for implantation, CL starts to form
Which cells of the ovary secrete progesterone and which pituitary hormone stimulates its production?
Corpus luteum -> made up of follicular granulosa cells FSH control
Which phase is dominated by ovarian secretion of progesterone?
Diestrus = low estrogen HIGH PROGESTERONE
Which cells in testes are the targets of FSH and LH?
FSH targets Sertoli cells (analogous to granulosa cells in ovary)- spermatogenesis LH targets Leydig cells (analogous to theca cells in ovary)- secretes testosterone and surrounds the seminiferous tubules
What are the two pituitary gonadotrophs?
Follicle stimulating hormone (FSH) Luteinizing hormone (LH)
Which cells of the ovary secrete estrogen and which pituitary hormone stimulates its production?
Follicular granulosa cells FSH stimulates it
What is proestrus?
HIGH estrogen -> stimulates endometrial proliferation FSH & LH stimulate follicular growth and production of estrogen. Estrogen supresses LH & FSH secretion (Negative feedback, mediated by GnRH) Low progesterone....
What is estrus?
High levels of estrogen stimulate LH surge (switches to positive feedback) the surge of LH triggers ovulation. Female is receptive to male
What is diestrus?
In pregnant females, the CL is rescued from regression by placental hormone chorionic gonadotropin. The CL is fully formed and secretes LOTS of progesterone
What is anestrus or pregnancy?
In the absence of pregnancy, the CL regresses as a consequence of locally released uterine prostaglandin F2alpha. The resulting decrease of progesterone levels removes LH and FSH inhibition and the cycle starts again.
What phase of the estrus cycle is dominated by ovarian secretion of estrogen?
Proestrus = HIGH ESTROGEN low progesterone
Describe granulosa cells:
They express FSH receptors synthesize ESTROGEN during follicular phase (proestrus/estrus) They produce PROGESTERONE during luteal phase (diestrus)
Describe Theca cells:
They express LH receptors they synthesize androgen during follicular phase (proestrus/estrus They switch to low level estrogen synthesis during luteal phase (diestrus)
Why is the change from the negative to positive estrogen feedback effect on gonadotropin release important for ovarian physiology and what are the consequences of this process for mature follicles?
When estrogen switches from negative to positive feedback it causes a surge of LH which triggers ovulation
What are the effects of estrogen and progesterone on the endometrium?
estrogen stimulates endometrial proliferation progesterone stimulates endometrial secretion to prepare for implantation and pregnancy
Which cells produce androgens?
follicular theca cells LH stimulates it -> converted to estrogen by theca cells
How would you describe the dynamics of gonadotropin release in males?
in males FSH and LH are released in a steady fashion to stimulate secretion of testosterone and estrogen to support continuous spermatogenesis
Which cells in the testes produce testosterone?
interstitial or LEYDIG cells
What does FSH stimulate?
maturation of ovarian follicles and estrogen production by granulosa cells
What are the function of the interferon tau?
produced by ruminant trophoblasts which tells the ovary the animal is pregnant and to keep the CL and keep secreting progesterone
What are the phases of the estrus cycle?
proestrus estrus metestrus diestrus anestrus (or pregnancy)
What is the function of relaxin?
relaxes pelvic ligaments and increases oxytocin synthesis in preparation for paturition
What are the functions of the placental chorionic gonadotropin?
rescues the CL from regression which keeps progesterone levels high
How does the hypothalamus and ovarian hormones know when to inhibit secretion of LH and FSH?
secretion is inhibited through negative feedback of estrogen for most of the estrus cycle. Also, progesterone inhibits FSH and LH secretion from anterior pituitary
How does the hypothalamus and ovarian hormones know when to secrete LH and FSH?
secretion is stimulated by GnRH from the hypothalamus and positive feedback of estrogen at end of proestrus, just before estrus
What is the function of placental lactogen?
supports maternal metabolism and initiates milk synthesis
What does LH do?
triggers ovulation and development of the corpus luteum, androgen production by theca cells
