FSH-Who control FSH secretion??

LH Hormone Basics.

 FSH & Inhibin B are not husband & wife bondage that will be in the same boat and of  same thought, beheaviour, culture , education , eating  habits !!!!! FSH release from pituitary is tonicaly   inhibited by inhibin B which is released from granulosa cells of follicles. If FSH level is found high then always think of something wrong in Ovaries primarily. By contrast , when you see an report of high LH  then consider  primary defect in hypo/ ant Pit. . The FSH level is primarily controlled by ovaries not by hypothalamus.

As  a woman ages or in cases of say failing ovarian reserve  (POF-DOR)  there will be less Inhibin B in circulation  due to less functioning of active granulosa cells in the gonads . Incidentally such granulosa cells also secrete AMH. We will discuss AMH in some other day.  However, in cases of POF/ aged women  as    FSH suppression by inhibin B is withdrawn as happens in cases of dwindling ovarian reserve, so level of basal FSH slowly rises. .Normally this is observed from late 4^th decade of life even in perfectly healthy parous women. . FSH rise will be slow but steady from age 35 yrs onwards. . Two consecutive FSH values on day 3 of spont period or day 5 of induced period = a FSH of > 10 ( at an interval of 3 months) means failing  Ovarian function and two reports  of (at an interval of 3 months)   > 20 warrants donor egg,  if couple is interested  in fertility.   “FSH-Inhibin B”  is a long loop suppression of FSH (both in males & females) .What is then  short loop control of FSH secretion from basophilic cells of adenohypophysis??  The short loop stimulation is by GnRH which however primarily looks after LH level and has poor control on FSH level.  Take home message:--if  FSH level is found high then always think of something wrong in Ovaries primarily . By contrast when you see an treport of high LH  then consider  primary defect in hypo/ ant Pit. . The FSH level is primarily controlled by ovaries not by hypothalamus.

What happens at Pituitary?? :-There  should be priming of Pit by E2 before Pit becomes eligible to response to GnRH.  This is more relevant in cases of LH release from Pit. With the advent of puberty there is sudden gain in ht & wt as such more peripheral oestrogens which help to make ant Pit celles sensitive to GnRH (LH RH) .Therefore in cases of Weight loss nervosa- there will be less LH release than FSH. By contrast in midcycle when serum level of E2 is highàthere will be more release of LH(Mid cycle  surge)->  Ovulation.

What are the causes of high LH??  Causes of high LH > 10 mIU/ml/= 1) Menopause, 2) PCOS  in about 40% of all PCOS. &  3) Midcycle surge. More is level of LH less will be chance of pregnancy. Therefore down regulation is often proposed. If Pre-induction by OCP/ Progesterone does not help. Whenever the LH level is below the level of < 2 mIU/ml/à it implies that the cause is either in Pituitary or in hypothalamus.(WHO Class I anovulation)

FSH	LH	E2	Etiology.
N	high	Usually N	PCOS
N	Low	Low	Weight related Ameno
Low	Low	Low	Functional/ organic HH
Raised	Raised	low	If associated with	Oligo/ameno	Then Ovarian failure
Elevated	Elevated	High	Most probably	Blood was drawn in	Midcycle.