Changes in serum LH concentrations during normal and abnormal sexual development in the pig

Abstract

Blood samples were collected from fetal and prepubertal pigs, starting at 49 days postcoitum and ending with pigs 25 weeks old. In addition, blood samples were collected from unilaterally cryptorchid, freemartin and castrated pigs of similar ages. Serum LH was quantified by radioimmunoassay. The LH concentration in the serum of male and female fetuses was undetectable in the second trimester of gestation but increased gradually thereafter, up to two weeks after birth. Frequent sampling of 2-week old pigs showed irregular LH peaks (>2ng/ml) at this time. In the third and fourth week after birth average LH concentrations decreased. Average LH concentrations increased to about 2 ng/ml in castrated pigs. LH concentrations observed for freemartin pigs were 1.3 ± 0.7 ng/ml. The changes in LH concentrations appeared to be well correlated with the differentiation and functional activity of the testis. No correlation could be detected between the changes in LH concentration and normal and abnormal gubernacular development.