Page 97 - Fertility in Women with Rheumatoid Arthritis Vruchtbaarheid van vrouwen met reumatoïde artritis

In agreement with the other study on AMH in established RA,8 we did not nd a signi cant association of AMH levels with disease duration. However, we did observe a signi cant association of lower AMH levels with the presence of ACPA, which has been related to a more severe disease responding poorer to anti-rheumatic therapy.38 Possibly women with more severe RA have high levels of circulating cytokines or immune cells affecting the ovaries during active disease, or the long-term use of anti- rheumatic drugs, such as methotrexate, affects the ovaries.39 However, no signi cant effect of past use of methotrexate on TTP in RA has been reported.2 Therefore, it will be interesting to analyze the effect of circulating cytokines and cumulative anti- rheumatic drug use on AMH levels in women with RA in future studies.
The comparison of AMH levels with controls has to be interpreted with caution.
As explained in the methods section, the AMH levels in controls were previously
measured using an assay by another manufacturer, and a conversion factor was
applied.29 The use of conversion formulae for comparison of AMH levels from different
assays has been debated. Especially with higher AMH levels, the precision of using
regression equations decreases.29 However, the number of patients in our study with
AMH levels around or above the 90th percentile of controls were low. Furthermore, the
focus of our current report is on the lower AMH levels, and therefore less precision loss 6 is to be expected. Indeed, using other conversion formulae that have been reported29
still showed signi cantly lower AMH levels in RA patients compared to controls. Another point of consideration is the lower limit of detection for the applied pico AMH assay. Replacement of very low AMH levels in our cohort with the conversed limit of detection of the older AMH assay used in the control group still showed signi cant lower AMH levels in RA patients compared to controls (p<0.001, data not shown).
Although AMH levels in RA patients were lower than in healthy controls, serum AMH levels did not show a signi cant association with TTP. The reduced AMH levels may be explained by a diminished number of ovarian follicles, but may also be the result of a reduced expression of AMH by the individual follicles. Either way, the reduced AMH levels in women with RA do not appear to have a signi cant effect on their conception chances. In a previous report that has shown low AMH levels to be a predictor of reduced fertility, selected patients were older, had been trying to conceive for a shorter period of time, pregnancy rates were higher, and AMH levels were dichotomized for analysis.23 Another report on healthy women of a younger age showed no reduced fertility when AMH levels were low.24 On the contrary, it did report an association of
AMH in RA – time to pregnancy
95