Thyroid hormone (TH) is important for normal reproductive functions and dysregulation of TH support is associated with reproductive disorders. We have previously reported that 3,5,3'-triiodothyronine (T3) increases follicle stimulating hormone (FSH)-induced preantral follicle growth in vitro. Interaction of hormones with apoptosis and proliferation of granulosa cells is poorly understood. The present study investigated the role and the mechanism of T3 and/or FSH on granulosa cell apoptosis and proliferation. Granulosa cells harvested from DES-primed immature rats were exposed to T3 (1 nM) and/or FSH (100 ng/ml) for 24-48 h. We demonstrated by TUNEL assays that the hormones prevented cells from C8-ceramide-induced apoptosis. The Src/PI3K/Akt pathway was involved in the regulation of granulosa cell survival. While ineffective alone, T3 significantly enhanced the proliferating cell nuclear antigen (PCNA) content of FSH-induced granulosa cells, consistent with the cell number pattern after treatment. Moreover, the action of the hormones on cell proliferation was also shown to be mediated by the Src/PI3K/Akt pathway. Taken together, these results suggest that T3 potentiates the cell survival action of FSH through inhibiting cell apoptosis and promoting cell proliferation. Moreover, the protective and survival effects of hormones are mediated by the activation of Src/PI3K/Akt pathway.