Less acidic forms of luteinizing hormone are associated with lower testosterone secretion in men on haemodialysis treatment

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Abstract
Summary: OBJECTIVE Men with chronic renal failure treated by haemodialysis have raised levels of bioactive LH (B‐LH) and immunoreactive LH (I‐LH) but reduced B‐LH: I‐LH (B: I) ratio and testosterone (T) secretion. This study investigated the LH isoform distribution in serum from normal adult males and males on regular haemodialysis treatment.DESIGN Four blood samples (2 ml) were obtained at 15‐minute intervals from a group of men on regular haemodialysis treatment. These samples were part of a larger pulse profile series and showed no evidence of LH pulsatility. The serum was pooled for each Individual patient. Blood (10 ml) was also drawn randomly from healthy male volunteers. The sera were chromatofocused on a 4‐ml mono‐P column attached to a fast performance liquid chromatography system. This procedure separates the LH isoforms according to their isoelectric point. The pH gradient was between pH 7 and pH 4.PATIENTS The five men with chronic renal failure were aged between 18 and 40 years and had been on haemodialysis for a mean of 10 months (5–20). They were sampled the night prior to a dialysis session. The five normal healthy volunteers had never had any endocrine disorder diagnosed.MEASUREMENTS An immunoradiometric assay and a commercially available (Delfia) immunofluorimetric assay were employed for detection of LH In the sera and in chromatofocusing fractions. B‐LH and testosterone were also measured in the sera.RESULTS Hormone data (mean±SEM for normal and renal subjects respectively) were 15.5 IU/I±1.2 and 26.9 ±7.2 (B‐LH), 6 0 IU/I±0.3 and 16.5±4.8 (irmaLH), 5.7 ±0.5 and 13.6 ±4.8 (lluorLH), 25.2nmol/l±2.0 and 12.1 ±1.2 (T). The serum B:l ratios were 2.6±0.1 and 2.6±0.2 (controls, irmaLH and fluorLH respectively) and 1.7 ± 0.1 and 2.1 ± 0.1 (chronic renal failure group). Recovery of LH from the column was 111 ±12% (mean±SEM)by IRMA and 104 ±7% by IFMA for the ten FPLC runs. The median pi for the LH distribution measured by both assays was in the region 6.54–6.40 for subjects with chronic renal failure and 6.09–5.95 tor controls. Median pi was negatively correlated to the B‐LH:irmaLH (P<0.0001) and B‐LH:fluorLH ratios (P = 0.002) in the serum. Furthermore, the proportion of isoforms recovered in the pH region 6.25–5.50 increased with increasing T levels in the serum (P<0.004).CONCLUSION The distribution of LH in serum of men on haemodialysis is more basic than in normal men. The greater the proportion of more acidic LH species, particularly those with a pi of between 5.50‐6.25, the higher the ratio of LH bioactivity to immunoactivity and consequently testosterone levels.

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