The effect of gonadotrophins with differing LH/FSH ratios on the secretionof the various species of inhibin in women receiving IVF

We have measured secretory patterns of inhibin A, B, total a inhibin, pro-a lphaC inhibin and oestradiol in women following pituitary suppression who w ere randomised into two groups to receive either urinary gonadotrophin (25: 75 IU/ampoule of luteinizing hormone (LH) and follicle stimulating hormone (FSH; Normegon; n = 11) or recombinant (r)FSH (75 IU/ampoule of FSH alone, n = 16), The women were of similar age (similar to 33 years) and length of infertility (similar to4 years) and had a normal endocrine evaluation, Plas ma FSH, LH, oestradiol, inhibin A, B, pro-alphaC and total alpha inhibin we re measured by immunoassay prior to and following gonadotrophin stimulation . Immunoactive FSH, LH and oestradiol blood concentrations following pituit ary down regulation were similar in the two groups being <2.0, <3.6 IU/I an d < 82 pmol/l respectively. The units of FSH given (2230 versus 2764 IU; No rmegon versus rFSH), duration of treatment (9.1 versus 9.4 days) and number of follicles of greater than or equal to 14mm on the day of human chorioni c gonadotrophin (HCG) administration (17 versus 14) were also similar. Inhi bin A or B concentrations rose similarly during Normegon or rFSH administra tion, peaking at days 9-11, Total alpha and pro-alphaC inhibin concentratio ns were lower (P < 0.05) in the rFSH group during days 10 and 11 of treatme nt being 18.9 +/- 15.9 ng/ml (Normegon) and 4.6 +/- 2.8 ng/ml (rFSH) for to tal a inhibin and 8.5 +/- 6.8 ng/ml (Normegon) and 2.8 +/- 1.6 ng/ml (rFSH) for pro-alphaC inhibin on day 10. Overall, higher total a inhibin concentr ations were associated with more mature follicles and oocytes, greater fert ilization rates and better quality embryos. We conclude that inhibin A and B secretion was similar in both groups and is primarily controlled by FSH, whereas total alpha inhibin and pro-alphaC increased preferentially in the Normegon group over the rFSH group, indicating that they are, in part, stim ulated by LH.