The effect of different exogenous hormone regimens on body weight in female hooded-Lister rats

JS Sutcliffe; KM Marshall; JC Neill

The aim of this study was to evaluate the effects of estradiol ± different progestogens on body weight in ovariectomised mature female hooded-Lister rats.

35 rats were ovariectomised under anaesthesia; following a recovery period animals were divided into 2 groups namely: (1) intermittent hormone dosing weeks 1–6 and 13–18, with no treatment weeks 7–12 and (2) delayed (no treatment in weeks 1–12) hormone treatment dosing weeks 13–18. The hormone regimens included vehicle (v) (1 ml/kg olive oil), 17-β-estradiol propionate (E) only (450 μg/kg weekly) and E (450 μg/kg weekly) plus medroxyprogesterone 17-acetate or d (-)-norgestrel (MPA or NOR 15 mg/kg every 2^nd week). Body weights for each animal were recorded and analysed with one-way ANOVA with post-hoc Dunnetts t-test, n=5.

Vehicle animals gained weight throughout the study. Hormone treatment attenuated the observed weight gain, with differences being more significant for group 1 animals.

Table 1 Body weights of hormone treated animals compared to vehicle animals at weeks 2, 7 and 19.
(Week) V	E (1)	E+MPA (1)	E+NOR (1)	E (2)	E+MPA (2)	E+NOR (2)
(2) 308±10	290±5	294±6	292±6	281±6	305±8	300±12
(7) 350±7	289±7**	296±7*	300±4*	368±11	371±14	338±19
(19) 396±10	320±7***	339±8**	342±7**	353±10*	360±12	333±21*
(P<0.05, P<0.01 and **P<0.001 Dunnett’s t-test).

The findings of this study point to a beneficial effect of exogenous hormones on body weight. Group 1 animals showed significant reductions in body weight when compared to vehicle animals, this being most evident in the E only group. Group 2 animals do show reductions in body weight although these reductions were less significant. In group 1 the progestogenic agent attenuated the effects of the estradiol alone but this was not seen in the group 2 animals.

Endocrine Abstracts

P110