Effects of luteinizing hormone-releasing hormone (LRH) upon bioactive and immunoreactive serum LH in patients with Turner's syndrome before and after oestrogen treatment.

Abstract

One daily dose of 0.05 mg ethinyl oestradiol was administered to 5 patients with Turner's syndrome (mean age +/- SEM = 16.4 +/- 0.7 years) for 10 days. The effects of acute stimulation with luteinizing hormone-releasing hormone (LRH) (0.1 mg iv) on biologically active and immunoreactive LH were analysed before therapy and at the end of oestrogen treatment. Bioactive LH (BIO-LH) was measured by a sensitive and specific in vitro bioassay based upon testosterone production by mechanically dispersed mouse Leydig cell preparations. Immunoreactive LH (RIA-LH) was evaluated by a double antibody RIA method. Prior to oestrogen treatment, LRH induced a prompt rise in BIO-LH and RIA-LH levels, which reached peak values at 30 and 45 min, respectively. After oestrogen treatment, a delayed response (with peak values at 120 min) was observed for both BIO-LH and RIA-LH. Before oestrogen treatment, the mean bioactivity to immunoreactivity (B/I) ratio of LRH-stimulated LH showed a significant decrease from basal values (P less than 0.05). In contrast, after ethinyl oestradiol administration the mean LH B/I ratio increased significantly from basal values in response to LRH (P less than 0.05). The mean relative maximum response (delta %) for BIO-LH was significantly higher (P less than 0.05) in oestrogen-treated than in untreated patients, whereas the mean BIO-LH delta area was significantly lower in the former group (P less than 0.01). Similarly, oestrogens decreased significantly the mean RIA-LH delta area (P less than 0.05), whereas they did not affect significantly the mean RIA-LH delta %. The results further emphasize that oestrogens may change the quality of circulating LH.