Dissociation of pituitary glycoprotein response to releasing hormones in chronic renal failure

The LH, FSH and TSH response to LRH and TRH has been evaluated in patients with chronic renal failure. Basal gonadotrophins were evaluated in 3 out of 6 males; one of 4 pre-menopausal females had increased basal LH. Exaggerated LH responses to LRH were noted in 4 out of 6 males and one of 4 females; FSH responses were increased in 3 of these males. One male and one female had attenuated LH and FSH responses to LRH. Both testosterone and oestradiol levels were reduced. In 5 out of 6 subjects tested both pre- and post-dialysis there was a greater LH and FSH response to LRH following dialysis. This suggests the presence of a dialysable toxin which is inhibiting the gonadotrophin response to LRH. Gonadotrophin levels remained elevated during 4 h of dialysis suggesting prolongation of the metabolic clearance rate. Despite low T3 levels, TSH response to TRH (200 μg) was only elicited in 2 of 6 cases. However, all 3 responded to 500 μg and 2 out of 3 to 1000 μg TRH, the third showing an attenuated response. TSH levels also remained persistently elevated in the responders. Dialysis, however, failed to improve the relative TSH non-responsiveness to TRH. In conclusion the data has shown that there is a dissociation in glycoprotein hormone responses to releasing hormones in uraemia. Whereas the gonadotrophs retain their responsiveness to LRH, the thyrotrophs appear to be more affected by the uraemic process and demonstrate an impaired response to TRH.