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Elevated LHRH levels in human milk
Anterior pituitary gonadotropins are regulated by the hypothalamic peptide hormone LHRH. However, the extrahypothalamic source(s) as well as extrapituitary action(s) of LHRH exist. We describe the discovery of relatively elevated levels of LHRH in human milk and its possible functions in the neonates. Blood and milk samples were obtained at the same time in post-partum period from lactating mothers. Special methods of extraction and concentration of milk as well as plasma LHRH were developed, and the hormone levels were determined by a sensitive double antibody radioimmunoassay using 125I-LHRH of high specific activity and immunoreactivity. Human milk contained 5 to 6 times more LHRH than plasma samples. The pure milk LHRH was fully biologically active when tested in vivo. Another hypothalamic hormone, TRH, is not found in such high concentrations in milk, only 5% that of LHRH. This excludes the possibility of an in vivo concentrating mechanism for the hypothalamic LHRH. Since LHRH neurons possess only minute amounts of the hormone, which is released in hypophyseal portal circulation, the large amounts present in the milk of lactating mothers may be of extrahypothalamic origin. Partial absorption of intact LHRH from intestine is known. The elevated levels of milk LHRH may have a profound influence in certain biological processes in the neonatal life, in continuation of the intrauterine exposure to high levels of LHRH of placental origin.
Anterior pituitary gonadotropins are regulated by the hypothalamic peptide hormone LHRH. However, the extrahypothalamic source(s) as well as extrapituitary action(s) of LHRH exist. We describe the discovery of relatively elevated levels of LHRH in human milk and its possible functions in the neonates. Blood and milk samples were obtained at the same time in post-partum period from lactating mothers. Special methods of extraction and concentration of milk as well as plasma LHRH were developed, and the hormone levels were determined by a sensitive double antibody radioimmunoassay using 125I-LHRH of high specific activity and immunoreactivity. Human milk contained 5 to 6 times more LHRH than plasma samples. The pure milk LHRH was fully biologically active when tested in vivo. Another hypothalamic hormone, TRH, is not found in such high concentrations in milk, only 5% that of LHRH. This excludes the possibility of an in vivo concentrating mechanism for the hypothalamic LHRH. Since LHRH neurons possess only minute amounts of the hormone, which is released in hypophyseal portal circulation, the large amounts present in the milk of lactating mothers may be of extrahypothalamic origin. Partial absorption of intact LHRH from intestine is known. The elevated levels of milk LHRH may have a profound influence in certain biological processes in the neonatal life, in continuation of the intrauterine exposure to high levels of LHRH of placental origin.