Women's Corner
Women's Corner
A) Intrauterine : the hypothalamo-pituitary-ovarian axis diffrentiates and functionsB) Infancy and early childhood :
In the first 3 months of life : Seperation of the newborn infant from maternal and placental source of estrogen , releases FSH and LH from the negative feedback mechanism, gonadotropin level starts to rise to reach the adult castrate level.
Infancy (till 2 years) : The elevated gonadotropins results in waves of follicular maturation and atresia leading to transient elevation of the estradiol level which in turn produces negative feedback decreasing the gonadotropins to a low level at the age of 2 years which is maintained till the age of puberty .
Early childhood : Low levels of GnRH , gonadotropins and estrogen
· The Gonadostat (hypothalamo-pituitary system controlling the GnRH/Gn) is 6-15 times more sensitive to the negative feedback .
· Intrinsic CNS inhibitor .
Late childhood (prepuberty) : What brings the onset of puberty ?
· Release of the inhibition of the gonadostat (decreased suppression) : be due to
- Decreased sensitivity of the hypothlamo-pituitary receptors to low estrogen levels
- Release of the inhibitory effect of the CNS intrinsic factor
- Reduction of melatonin (doubtful) : Released from the pineal gland which is stimulated by light, decrease the CNS intrinsic factor . Thus blind girls may have precocious puberty
· Gonadarche : As a result of release of the gonadostat from inhibition , the GnRH starts to increase first at night leading to mid-night pulses of LH and moderate rise of FSH which stimulates release of estradiol .
· Adrenarche : The postulated mechanism is
- Pituitary adrenal-androgen-stimulating factor (from preopio-melano-cortin) stimulates the adrenal gland to produce DHA, DHAS and androstenedione leading to adrenarche .
- Begins 2 years earlier than the gonadarche .
dr. Hisham Al-Inany Lecturer in Obstetrics and Gynecology Department, Cairo University, Egypt Dr. Amr Hussein Lecturer in Obstetrics and Gynecology Department, Cairo University, Egypt