Immunoextracted calcitonin in milk and plasma from totally thyroidectomized women. Evidence of monomeric calcitonin in plasma during pregnancy and lactation

Abstract

Abstract. The level of immunoreactive calcitonin in the first produced breast milk was in totally thyroidectomized (TX) women 713 ± 307 pg-eq/ml (mean ± sd, N = 7) and in control women 772 ± 329 pg-eq/ml (N = 33), i.e. about 45 times higher than in plasma (see below). On gel chromatography of immunoextracted milk from TX women, immunoreactive calcitonin appeared as high molecular weight forms in the same pattern as in milk from healthy women when the same antiserum (1) was used for immunoextraction and radioimmunoassay (RIA). In another series of experiments, a new antiserum (2) raised in rabbits was used for measurement of immunoreactive calcitonin after immunoextraction with 1. Plasma levels of immunoreactive calcitonin in the TX women during pregnancy were 16 ± 6 pg-eq/ml (N = 6) and during lactation 14 ± 7 pg-eq/ml (N = 5). Immunoreactive calcitonin was undetectable (< 8 pg/ml) in plasma from those TX women in whom lactation had stopped (N = 5). Immunoextraction and gel chromatography of plasma collected during pregnancy and lactation from the TX women showed that the immunoreactive calcitonin present eluted in the region of monomeric calcitonin with both antiserum 1 and 2. In conclusion, high concentrations of high molecular weight forms of immunoreactive calcitonin have been demonstrated in milk from TX patients, most probably devoid of any calcitonin-producing thyroid C-cells. This points to a local production site in the mammary gland. Relatively high levels of immunoreactive calcitonin in plasma during pregnancy and lactation in TX women also indicate extrathyroidal production.