Thyroid stimulating hormone causes cumulus expansion in mouse oocytes

The objective of this study was to determine if thyroid stimulating hormone (TSH) could induce cumulus expansion in mouse oocytes in-vitro. The effect of TSH was compared with the effects of LH and FSH. Oocytes were incubated in minimum essential medium (MEM) with and without hormones for 16 h at 37 degrees C under a humidified atmosphere of 5% CO(2) and 95% air. Then LH, FSH or TSH was added into the culture medium at a concentration of 0.25, 0.5, or 1.0 mug/ml, respectively. Cumulus expansion was scored in a subjective manner (O = no expansion; + = slight; ++ = moderate; +++ = maximum expansion) 16 h after addition of the hormones. The percentage of oocytes in the 4 categories of expansion was noted; LH failed (P>0.05) to induce cumulus expansion while TSH and FSH induced cumulus expansion (P<0.05) at all of the doses tested. For FSH, the 0.5 mug/ml dose showed the best response (26% = 0; 18% = +; 10% = ++; 46% = +++). For TSH, the 1.0 mug/ml dose showed the best response (38% = 0; 18% = +; 13% = ++; 31% = +++).