Lactation and pregnancy in Iran. III. Hormonal factors.

Lactation failure is common in urban areas of industrially developing countries, but little is known about its epidemiology and causality. The study reported here was undertaken to investigate the serum levels of some hormones other than prolactin that have been shown in animal studies to play a role in lactation, and to examine their relationship to adequacy of lactation and to nutritional and socioeconomic status in urban Iranian women. Serum levels of placental lactogen, growth hormone, cortisol, and thyroid hormones were measured under standard conditions in two groups of pregnant women from low and low middle socioeconomic areas of Teheran, 1 or 2 weeks before parturition and the latter three hormones again in the 3rd month postpartum. Significant differences were found in the biochemical parameters between socioeconomic groups. Hemoglobin and serum albumin values were lower and all the globulin fractions (except alpha 2 globulin during pregnancy), growth hormone and cortisol were higher in the low than the middle socioeconomic subjects, both during pregnancy and postpartum. The discrepancies between the socioeconomic groups were greater postpartum. Growth hormone level was significantly lower in subjects with adequate lactation than inadequate or ceased, and cortisol values show the same trend. No correlations were found between the measured parameters of nutritional status nor free thyroxine values and lactation adequacy. In view of the role of growth hormone and cortisol in stress and malnutrition and some evidence of a reciprocal relationship between growth hormone and prolactin, these hormones may be a link in the chain between the urban environment, malnutrition and lactation failure.