Suppression of normal and preneoplastic mammary growth and uterine adenomyosis with reduced growth hormone level in SHN mice given monosodium glutamate neonatally.

As a step in the evaluation of the role of growth hormone (GH) in mammary tumorigenesis, the effects of neonatal treatment with monosodium glutamate (MSG) on normal and neoplastic mammary growth, plasma levels of GH and prolactin (PRL) and the pattern of estrous cycles were determined in SHN virgin mice. The development of uterine adenomyosis, which is under similar hormonal control, was also examined in these mice. The formation of precancerous mammary hyperplastic alveolar nodules (HAN) was markedly inhibited and the number of 'ghosts', the remnants of regressed HAN, was increased by the single injection of 4 mg MSG on the day of birth, although spontaneous mammary tumorigenesis was not inhibited. The incidence of adenomyosis was suppressed by MSG treatment. Plasma GH level was chronically lower in the MSG-treated mice than in the controls. In contrast, plasma PRL levels and the pattern of estrous cycles were little affected by the treatment. These results indicate an involvement of GH in the development of HAN and uterine adenomyosis in mice.