Female Reproductive Endocrinology and reproductive cycle Flashcards
From which molecule are steroid hormones synthesised from?
Cholesterol
Where are steroid hormones mainly produced?
Adrenal glands
Gonads
Placenta
Why is it important that steroid hormone receptors have a high affinity and specificity to their substrates?
Steroid hormones are present in low concentrations in serum and tissues
Where in the cell does steroid hormone production primarily occur?
Smooth ER and mitochondria
Steroid hormones are stored. T/F?
False
What is the intermediary in the synthesis of progesterone from cholesterol?
Pregenolone
What symptoms may result from a deficiency of 21-hydroxylase or 11beta- hydroxylase?
Ambiguous genitalia
Precocious ouberty
Anovulation
Hirsutism
What eefct will aromatase excess have in a male?
Conversion of androgens to oestrogens resulting in feminisation of male genetalia
What types of hormones are GnRH, FSH and LH?
Peptide hormones
Where is GnRH secreted from?
Hypothalamus
Where are FSH and LH secreted from?
Anterior pituitary gland
What are the three phases of the ovarian cycle and at what days in the female reproductive cycle do these occur?
Follicular phase days 1-13
Ovulation day 14
Luteal phase days 15-28
What are the three phases of the uterine cycle and at what days in the female reproductive cycle do these occur?
Menstruation days one to five
Proliferative phase days 6 to 14
Secretory phase days 15 to 28
At the start of the female reproductive cycle, progesterone and oestrogen levels are low. Why is this significant?
This stimulates GnRH release from the hypothalamus which stimulates the gradual release of LH and FSH from the anterior pituitary which stimulates follicle growth and development
How does the developing follicle in the ovary produce oestrogen?
The theca cells are stimulated to produce androgens by LH and the granulosa cells pick up these androgens and convert them via aromatase to oestrogens under the influence of FSH
Why is there a dip in Lh and particularly, FSH, levels before ovulation?
Because the now increasing concentration of oestrogen is stimulating production on LH and FSH but inhibiting secretion and furthermore, inhibin is being released from granulosa cells to inhibit FSH secretion
When oestrogen reaches a critical level this stimulates massive rapid release of LH. What event does this stimulate?
Ovulation
What are the effects of oestrogens from the ovary on the endomterium during the proliferative phase?
Thickening of endometrium
Elongation of uterine glands
Growth of coiled arteries in stratum functionalis
Which hormone is primarily secreted by the corpus luteum?
Progesterone
Why is LH and FSH secretion decreased in the luteal phase?
High circulating levels of progesterone, oestrogen and inhibin are inhibiting FSH and LH synthesis in the anterior pituitary
What hormone, released from the early embryo, will result in the maintenance of the corpus luteum if pregnancy occurs?
Human chorionic gonadotrophin
If pregnancy does not occur progesterone levels will decrease towards the end of the luteal phase. Why is this?
Because if pregnancy does not occur then after about ten days the corpus luteum will degenerate and so stop secreted progesterone
How does cervical mucous comsistency change during the female reproductive cycle?
In the late follicular phase under the rising levels of oestrogen, the cervical mucous becomes more watery to allow the passage of sperm
In the luteal phase, progesterone levels increase and this causes thickening and reduced elasticity of the cervical mucous
Describe the mechanism of action of the combined contraceptive pill
This comtains oestrogen and progesterone wwhich have a negative feeback effect on tthe hypothalamus and anterior pituitary to prevent GnRH, LH and FSH release to prevent ovulation
The progesterone also results in thick, non elastic cervical mucous