Effects of age and parity on serum hormone levels in the FVB/N-RC mice.

Serum was collected from 14-wk-old females, aged-nulliparous and aged-multiparous females and analyzed for the indicated hormones as described in Materials and Methods. No significant difference was observed in the serum levels of estrogen, thyroxin (T4), growth hormone (GH) or bioactive prolactin. Triiodothyronine (T3) was significantly higher in serum samples of the aged-nulliparous (*PP* = P**Serum levels of bioactive prolactin are measured in ng/ml.