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
Describe the mechanism of action of the progesterone only contraceptive pill
This results in thickening of the cervical mucous
What conditions may cause an excess of female reproductive hormones?
Polycystic ovarian syndrome
Granulosa cell tumour
Teratoma
What conditions may cause a defeciency of female reproductive hormones?
Hypogonadism Turners syndrome Klinefelters syndrome Kallmans syndrome - GnRH defeiciency Hypopiyptuitarism
What are the symptoms of polycystic Ovarian syndrome?
Infertility Lack of ovulation Lack of menses Weight gain Hirsutism Acne
What will be the ratio of Lh:FSH in polycystic ovarian syndrome?
Over 2:1
Outline the process of oogenesis
During early female development, primordial germ cells called oognia migrate into the ovarian cortex and multiply by mitosis. By the fourth and fifth months of gestation some of these oognia enlarge and assume the potential to become mature gametes. These are primary oocytes which are held in prophase I of meiosis I by their encapsulation by follicular cells. These cells do not develop any further until puberty when the process of meiotic division and follicular development occurs in the lead up to ovulation and fertilisation
Why is it that several primary follicles begin development each month but only one follicle fully matures?
The reasoning behind this apparent wastage is unclear however since the follicles have an endocrine role during their development, it is thought that perhaps one single follicle would be unable to satisfy the level of endocrine function required and so the other follicles may in fact by acting primarily as endocrine glands
Describe the development of a primordial follicle into a primary follicle?
This still contains a primary oocyte but this is now surrounded by a single layer of supportive follicular cells which begin to secrete fluid into the interstitial space. The stomal cells surrounding the folicle also start to condense to form theca folliculi. A zona pellucida starts to form around the primary oocyte
Describe the development of a primary follicle into a secondary follicle?
The secondary follicle is larger and the follicular fluid builds up to produced a fluid filled space which partially surrounds the primary oocyte called the antrum. The theca folliculi forms an interna layer responsible for androgen production and a collagenous externa layer. The corona radiatae also starts to form - a condensed ring of granulosa cells which adhere tightly to the zona pellucida of the oocyte
Describe the development of a secondary follicle into a Graafian follicle?
The oocyte becomes a secondary oocyte as it completes its first meiotic division and starts the second meiotic division, remainin gin metaphase until fertilisation. The mature follicle will rupture and this is ovulation
What is the coprus luteum?
The remnant of the ruptured follicle present in the cortex of the ovary that consists of a tightly folded, thick epithelium surrounding a central cavity which contains a blood clot and this acts as a temporary endocrine gland
What structure is the remnant of the corpus luteum?
Corpus albicans
How long is the average female reproductive cycle?
28 days
Explain the physiology behind the loss of the stratum functionalis in menstruation?
If pregnancy does not occur then the corpus luteum will degenerate approximately ten days after ovulation. This results in a decrease in progesterone (as the corpus luteum no longer exists to secrete progesterone) and the stratum functionalis, because of this lack of progesterone, shrinks. Because the arteries in the statum functionalis are coiled, the arteries are compressed by this shrinkage and this leads to ischaemia and cell death. Thus, the stratum functionalis is lost during menstruation
In the secretory phase, what substance is secreted from the uterine glands to provide sustenance for the embryo should it implant?
Glycogen
