Objective: Insufficient breast milk is the most common reason for premature termination of breast-feeding. The causes of lactation insufficiency are usually multifactorial; in a small percentage of cases it is due to primary lactation failure of unknown origin. The aim of this study was to investigate whether lactation insufficiency of unknown origin could be caused by serum lactogens that had reduced biological activity.
Design: Women with lactation insufficiency of unknown origin and normal lactating controls were subjected to a standardized breast-feeding test for assessment of milk production. Thirty minutes later, serum samples were obtained for determination of total lactogen bioactivity, using an in-vitro bioassay, and levels of prolactin (PRL) and growth hormone (GH) using radioimmunoassay (RIA).
Patients: Twelve lactating mothers with a clinical diagnosis of lactation insufficiency of unknown origin were compared with 12 matched mothers with normal lactation.
Measurements: The Nb2 lymphoma cell bioassay was used to measure total lactogen bioactivity in sera. Conventional RIA kits were used to estimate serum PRL and GH concentrations.
Results: Mean milk yield on standardized test feed was 21.6 ml for patients and 146.5 ml for controls. In both patient and control groups the total serum lactogen bioactivity ranged from about 150 to 5000 mIU/l, while the serum RIA (PRL+GH) levels ranged from about 350 to over 7000 mIU/l. There was no evidence of lactogens with reduced bioactivity in the patients' sera.
Conclusion: Lactation insufficiency in the women studied cannot be explained by serum lactogens that possess unusually low bioactivity.