The possible role of corticosterone in regulating sodium and potassium concentrations in human milk

The aim of the study was to find the presence of corticosterone as a regular human milk constituent. We have evaluated the correlation of concentrations between the analyzed hormone and sodium and potassium in breast milk and serum.

Hand expressing breast milk samples and median cubital vein blood samples had been taken from 69 healthy, lactating women in early puerperium period (between the 3rd and 10th day) twice, before and after breastfeeding. Corticosterone concentrations in human plasma and breast milk were determined by radioimmunoassayed method. Direct assays were performed before and after breastfeeding, twice. The serum and milk sodium and potassium concentrations were estimated by Flame Emission analyzer CIBA-Corning 480, equipped with an automatic diluter.

Corticosterone was found in all milk samples, which is an original observation, and its concentration in milk was a few times lower than in serum. Its concentration values in human serum when were not higher than 3 nmol/L (n = 108) positively correlated with its concentrations in milk, and those exceeding 3 nmol/L (n = 30) have demonstrated a negative correlation. An original finding has shown a positive correlation between concentrations of corticosterone in human serum and of potassium in human milk (r = 0.018, p < 0.03). An attempt was also made to determine the presence of aldosterone in breast milk, but the radioimmunoassay did not reveal its presence.

The results confirm a relation between potassium concentration in milk and serum corticosterone concentration delivered to mammal gland with blood.