Striatal dopamine transporter availability with [123I]beta-CIT SPECT is unrelated to gender or menstrual cycle

The effect of gender and female menstrual cycle on human striatal dopamine transporters (DATs) was investigated with single-photon emission computed tomography (SPECT) using the ligand 2beta-carbomethoxy-3beta-(4-[(123)I]iodophenyl)tropane.

Ten female subjects aged 18-40 years (25.3+/-7.3 years) were scanned twice during the early follicular and the mid-luteal phases to detect any hormone-mediated changes in DAT availability in the striatum or serotonin transporter (SERT) availability in brainstem-diencephalon. Plasma estradiol and progesterone levels were obtained at the time of SPECT and confirmed the expected increases from the follicular to the luteal phases. Finally, in a post hoc analysis of a previously published healthy-subject sample, striatal DAT availability was compared between 70 male and 52 female subjects who ranged in age from 18 to 88 years.

In the ten menstrual cycle subjects, DAT availability (V(3)'') in striatum and SERT availability in brainstem-diencephalon did not differ between follicular and luteal phases. Moreover, change in V(3)'' for striatum or brainstem-diencephalon was uncorrelated with change in plasma estradiol or progesterone from the follicular to the luteal phase. In the larger healthy-subject sample, there was no significant effect of gender or the interaction of age and gender on striatal V(3)''.

These findings suggest that in using DAT or SERT ligands in the study of neuropsychiatric disorders, matching of female subjects according to a menstrual cycle phase is unnecessary. Although the present investigation did not confirm previous reports of gender differences in striatal DAT availability, controlling for gender in such studies still seems advisable.