HETEROLOGOUS RADIOIMMUNOASSAY FOR PLASMA HUMAN PROLACTIN (hPRL); VALUES IN NORMAL SUBJECTS, PUBERTY, PREGNANCY AND IN PITUITARY DISORDERS

Abstract

ABSTRACT A heterologous radioimmunoassay for human prolactin (hPRL) was developed, using a rabbit anti-ovine PRL (oPRL) which cross-reacted with hPRL and hPRL (Lewis 203-1) as tracer and standard. The sensitivity (0.02 ng hPRL) and the values obtained were comparable to those in homologous assays. When the immunoreactivity of a variety of hPRL preparations was compared, Friesen-71 hPRL was the most immunoreactive preparation, Lewis 203-1 and 201-195-1 hPRL had 75.6%, Friesen-C hPRL 54.4 %, and the Medical Research Council Standard (# 71-222) 27.5% of the immunoreactivity of Friesen-71 hPRL. hPRL content in 6 hGH preparations ranged from 0.001 to 0.2 %. Antibodies to hPRL were detected in 2 anti-hGH sera. The mean concentration of plasma hPRL in adult females (8.5 ± 1.5 ng/ml ± se) was significantly higher than in males (5.2 ± 0.5; P = 0.025). Plasma values of hPRL in girls between 4 and 17 years of age (7.2 ± 0.5) were not significantly different than in boys of the same age (6.0 ± 0.5). No variation in basal levels was found during puberty in girls, or with age in boys. The concentration of plasma hPRL was increased in pregnant women, newborn infants and in patients with galactorrhoea. Anencephalic infants had hPRL levels comparable to healthy newborns. The mean concentrations of plasma hPRL in patients with idiopathic isolated hGH deficiency or with idiopathic multiple pituitary hormone deficiencies were significantly higher than in normal subjects. Low to normal basal levels were measured in patients with hypothalamic tumour. Eight of 22 acromegalic patients had elevated hPRL levels; 5 female acromegalics had a significant rise in plasma hPRL values following injection of synthetic thyrotrophin releasing factor (TRF), but no increase after luteinizing hormone releasing factor (LRF). In conclusion, the heterologous radioimmunoassay for hPRL, using an anti-oPRL serum, has the requisite specificity, sensitivity, precision and reproducibility for clinical use.