Exogenous growth hormone treatment alters body composition and increases natural killer cell activity in women with impaired endogenous growth hormone secretion

Abstract

In order to assess the potential relationship between human growth hormone (GH) and body composition (BC) and natural immunity (NI), we measured the effects of exogenous GH on fat weight (FW), fat-free weight (FFW), and the cytotoxic activity of natural killer (NK) cells in women with impaired GH secretion. Mean peak serum concentrations of GH in response to l-dopa/arginine stimulation were 6.2 ± 1.1 (SEM) ng/mL in 6 untreated subjects (US) and 5.4 ± 1.5 ng/mL in 6 GH-treated subjects (TS). Moreover, the pretreatment circulating levels of IGF-I were low in both groups (US 684 ± 121 mU/mL and TS 583 ± 83 mU/mL), and they correlated with pretest levels of NK cell activity ( r = .59, P < .05) when both groups were combined. The TS were given 700 μg of human GH IM for an average of 14 days while the US were studied in parallel without GH treatment. As measured by hydrodensitometry or skinfold anthropometry, FW decreased (26.1 ± 6.8 kg to 23.8 ± 6.3 kg, P < .05) and FFW increased (44.9 ± 3.3 kg to 46.2 ± 3.8 kg, P < .05) in the TS. In the US, there were no significant ( P > .05) changes in either FW or FFW. Using a standard 51Cr release assay to measure the specific lytic (SL) activity of NK cells, mean SL activity increased from 24.4 ± 7.0% to 44.1 ± 8.9% ( P < .05) in the TS, whereas levels in the US were not altered significantly ( P > .05). We conclude that daily exogenous GH treatment favorably influences BC and increases NK cell activity in women with an impaired secretion of the hormone.