Placental protein 14 and pregnancy-specific β1-glycoprotein in women with suppressed, normal and stimulated follicular maturation

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Abstract
Not only the ovarian steroids but a number of proteins have an effect on the endometrium and its capability to accept an implanting embryo and to establish a pregnancy. In this study we have selected the placental protein 14 (PP14) which is, in spite of its name, produced by the glandular epithelium of the endometrium. Pregnancy-specific β1 -glycoprotein (SP1) was also investigated. This marker is trophoblast-specific but it has been chosen since some patients repeatedly exhibit weak but detectable serum SP1 when no embryo is present. There seems to be a negative correlation between the chance of obtaining a pregnancy and the occurrence of such abnormal serum SP1 signals; they could originate from the endometrium itself or from another maternal source influencing the endometrium indirectly. The full-cycle time course was determined for these two proteins as well as for estradiol and progesterone. A total of 66 cycles were analyzed, of which 16 were from ovulating volunteers without any hormonal treatment (controls) and 13 were from women taking oral contraceptives. The remaining 37 cycles were from 32 patients undergoing conventional in vitro fertilization (IVF) treatment. Eight pregnancies were achieved in this group during the study period. We found that abnormal positive SP1 signals occurred predominantly in the unsuccessful IVF subgroup, but also in the control groups (with or without contraceptive pills), and this in a cycle-independent manner. PP14, on the other hand, exhibited cyclic patterns in the IVF and ovulating control cycles as did progesterone. However, in seven out of 13 cycles under oral contraception (and suppressed progesterone), a mid-cycle rise in PP14 was observed. Moreover, midcycle PP14 levels were generally higher in this group when compared to the ovulating controls as well as to the cycles under controlled ovarian stimulation for IVF. This confirms that PP14 is influenced by progesterone but only in an indirect way or under the additional effect of other hormones. It is unlikely that SP1 plays this role since it was not correlated to any of the other proteins or steroids studied. Nevertheless, SP1 did not occur randomly over the different groups.