Table 1.

Plasma E2 and P4

Treatment	E2 (pg/ml)	P4 (ng/ml)
Placebo	12 ± 5	2.5 ± 0.9
E2	47 ± 11a	2.3 ± 0.7
P4	3.8 ± 1	16 ± 4.3b
E2+P4	29 ± 6a	15 ± 2.7b

Hormones assayed in a pilot study used the same lot of pellets and treatment paradigm with eight rats per group. The RIA sensitivity (Materials and Methods) does not allow statistical distinction of E2 levels between the E2 and P4 replacement groups. The pilot also showed that the initial surge of P4 from the implants subsided after 3 d, consistent with another study (44). 

^aP < 0.05, different from placebo and P4. 

^bP < 0.05, different from placebo and E2.