A 21 year old thoroughbred mare with granulosa theca cell tumor (GTCT) in the right side and atrophic contralateral ovary was investigated in this study. After arrival at our laboratory on 10th December 1999, the clinical diagnosis of GTCT was examined by rectal palpation and ultrasonographic image of ovaries. Plasma from peripheral blood was collected in the breeding and non-breeding seasons for hormonal analysis. The results showed that the contralateral ovary regained normal activity without any treatment of the GTCT affected ovary and contained follicles showing different sizes 19 months later. However, the affected right ovary, which became smaller after 4 months, was totally inactive without any follicle. The observations clearly demonstrate that without any treatment of the GTCT affected ovary, a mare can return to her normal estrous cycle within a certain period in some GTCT cases.
2003 by the Japanese Society of Veterinary Science