Uterine atrophy is a conspicuous finding in Nya:NYLAR female mice chro
nically infected with Toxoplasma gondii. Administration of 17B-estradi
ol to infected mice induced a vigorous uterotropic response, i.e., an
increase in uterine weight, in endometrial hypertrophy and proliferati
on, and in the activity of three estrogen-regulated uterine enzymes. T
hese findings rule out a parasite-induced refractoriness of the uterus
to estrogen and point to ovarian dysfunction (hypogonadism) as the im
mediate cause of the uterine atrophy.