Influence of medroxyprogesterone acetate (Provera) on plasma growth hormone levels and on carbohydrate metabolism. II. Studies in the ovariohysterectomized, oestradiol-primed bitch.

The combined effects of oestradiol and medroxyprogesterone acetate on growth hormone (GH) levels and carbohydrate metabolism were studied in 6 ovariohysterectomized dogs, which previously had shown moderate increments in GH after medroxyprogesterone acetate (MPA) administration. Oestradiol (Oe2) implants were administered 5 months after the last MPA injection, when MPA and GH levels tended to decrease. Following Oe2 administration GH levels rose significantly. Single MPA injections (100 mg) given 20 days after Oe2-priming were followed by still further increased GH levels. These GH levels were several-fold higher than GH levels achieved by previous MPA administration alone. GH levels decreased in 3 dogs after 35 days and remained elevated in the other 3 dogs as long as 70 days after MPA administration with Oe2 priming. Glucose assimilation became impaired and insulin response to a glucose load increased in relation to elevated GH levels. Oe2-primed control dogs, which received no MPA, failed to develop elevated GH levels. These findings indicate (1) that Oe2 and MPA induce overproduction in ovariohysterectomized dogs synergistically (2) that GH levels of the magnitude evoked are associated with glucose intolerance and insulin resistance.