Effects of hormone administration on milk production of underfed rats

¹ Department of Physiology and Pharmacology, Michigan State University, East Lansing, Michigan

Attempts were made to determine whether the reduction in milk output induced by underfeeding could be overcome by administration of hormones. Half-fed female rats were injected daily with one of the following preparations, from the 4th–17th days postpartum: 15 or 25 mg anterior pituitary powder; 1 mg growth hormone; 10 µg thyroxin/100 g body wt.; 0.5 or 1 mg cortisol acetate; 1 mg prolactin; 1 IU oxytocin; and the latter three hormones in combination. None of the hormones significantly increased litter weight gains, although cortisol acetate, prolactin, and oxytocin each produced slight gains during the later part of the lactation period. These results indicate that the decrease in milk production associated with underfeeding is due primarily to nutritional inadequacy and not to reduced endocrine function. It is believed that the suckling stimulus maintains the secretion of the hormones essential for milk production and removal at optimal or near optimal levels, even in the absence of adequate food intake.