1.5.3 Female Endocrinology, Pt 2 Flashcards
Answer these!
One of the initial changes prior to puberty is?
Nocturnal increases in gonadal steroid secretion
How do steroidal contraceptives work?
What are the characteristics of the luteal phase of the ovarian cycle?
- LH stimulates luteal cell progesterone and estrogen production
- Rising levels of ovarian steroids have a marked negative feedback effect on the GnRH pulse generator and gonadotropin production and lead to the eventual regression of the corpus luteum (removal of a luteotropin)
What occurs during menopause
- Reproductive senescence in the female is referred to as menopause. Associated with a lack of cyclicity and generalized ovarian hypofunction.
- The reduced ovarian function results in lower levels of steroid hormones and reduced negative feedback effects on the hypothalamic-pituitary axis. This leads to elevated levels of circulating LH and FSH.
- The amenorrhea associated with menopause is preceded by irregular cyclicity suggesting an alteration in the communication between ovaries, pituitary and hypothalamus.
- Distinct changes occur at the ovarian, pituitary and hypothalamic levels. There is a depletion of primordial follicles in the ovary but simply exhausting the supply of oocytes does not appear to be the entire answer.
Describe the pulsation of GnRH and FSH/LH during the luteal, follicular, and gonadotropin surge
The gonadal steroids regulate gonadotropin secretion
Hypothalamus – changes in GnRH pulsatility
Pituitary – associated changes in LH/FSH pulsatility
Inhibin/Activin also play a role in regulating FSH secretion
What is the process of follicle selection and atresia?
FOLLICULAR SELECTION AND ATRESIA
- Generally, one follicle is selected to ovulate per cycle. [Additional follicles can be ovulated by hyperstimulation with gonadotropins].
- The selected follicle achieves the greatest vascular supply and the greatest responsiveness to FSH. [Such a response is imperative in that FSH decreases from the rising estrogen and its negative feedback actions on FSH]
- Atresia arises by failure to acquire sufficient responsiveness to FSH.
- Atresia is promoted by increased accumulation of intraovarian androgens [especially nonaromatizable androgens such as dihydrotestosterone, DHT]
- Atresia is the fate of most follicles.
- May take 100-110 d to build an antral follicle (3-4 cycles).
What are the characteristics of the follicular phase of te ovarian cycle?
- Associated with follicle growth and increasing estrogen synthesis
- Follicular growth is dependent upon gonadotropins and estrogen
- Rising estrogen levels have a negative feedback effect on the GnRH pulse generator (medial basal hypothalamus/arcuate nucleus)
Describe the H-P-G axis at puberty
What are the characteristics of the proliferative phase of the uterine cycle?
- Associated with the follicular phase of the ovarian cycle
- Rising estrogen stimulates uterine endometrial cell proliferation
- Estrogen also affects the consistency of cervical mucus (faciliating sperm penetration)
Describe the H-P-G axis for an adolescent
What are the characteristics of Kallmann syndrome?
What are the characteristics of the secretory phase of the uterine cycle?
Associated with the luteal phase of the ovarian cycle
Rising progesterone levels stimulate:
uterine gland development
growth and development of the uterine vasculature
What are the characteristics of the ovulatory phase of the ovarian cycle?
As estrogen levels rise they reach a threshold for a positive feedback effect on gonadotropin secretion. Mediated by:
- increased responsiveness of gonadotropes to GnRH
- activation of GnRH neurons in the preoptic area of the hypothalamus
LH surge stimulates ovulation, removal of the meiotic block, and luteinization
What are the characteristics of the menstrual phase of the uterine cycle?
Associated with regression of the corpus luteum and declining progesterone and estrogen levels
Removal of the trophic steroids results in a lack of support for the endometrium and a sloughing off of the superficial layers
What are the changes in gonadotropin secretion in puberty?
Describe the H-P-G axis in children in regards to FSH/LH and estradiol
What are some important female reproductive disorders?
How can body size affect reproduction?
How do GABA and neuroexcitatory amino acids change from childhood to puberty?
During the luteal phase what are the main regulators?
Gonadotropin regulation of the Ovary
Following the LH surge and Ovulation:
- Cellular differentiation and tissue reorganization leading to formation of the CL.
- The CL is predominantly regulated by LH
- Stimulates progesterone secretion (estrogen and inhibin also)
- Luteolysis ensues due to a loss in gonadotropin support (roles for PGF2alpha and Oxytocin)
