Relationship Between 24-Hour Serum LH and Testosterone Concentrations and Their Interrelationships With Other Pituitary Hormones in Healthy Older Men

Abstract Background: With ageing, LH levels rise while T levels decline in men, although this decline in T levels could also be caused by a change in health status, including body composition, inflammation, and comorbidities. Not only levels of LH and T change with age, but levels of other pituitary hormones also change concomitantly with age. It could be hypothesized that these hormonal changes are synchronized with each other. Objective: In this study, we aimed to determine the relationship between 24-h serum LH and T concentrations in healthy older men. Besides, we aimed to determine which health factors, including body composition, metabolic and inflammatory markers, and LH-T related markers are associated with the strength of this LH-T relationship. Furthermore, we explored the interrelationships between LH and T with 24-h serum concentrations of GH, TSH, cortisol, and ACTH. Design: Hormones were measured in serum samples collected every 10 min during 24 h from 20 healthy men, comprising 10 offspring of long-lived families and 10 control subjects, with a mean (SD) age of 65.6 (5.3) years. We performed cross-correlation analyses to assess the relative strength between two 24-h hormone concentration series for all possible time shifts. Results: A mean (95% confidence interval) maximal correlation coefficient of 0.21 (0.10 – 0.31) at lag time 60 min was found between LH and total T concentrations. Results were comparable for calculated free, bioavailable, or secretion rates of T. Men with strong LH-T cross-correlations had, compared to men with no LH-T relationship, lower fat mass (18.5 (14.9 – 19.7) vs. 22.3 (18.4 – 29.4) kg), waist circumference (93.6 (5.7) vs. 103.1 (12.0) cm), hsCRP levels (0.7 (0.4 – 1.3) vs. 1.8 (0.8 – 12.3) mg/L), IL-6 levels (0.8 (0.6 – 1.0) vs. 1.2 (0.9 – 3.0) pg/mL), and 24-h mean LH levels (4.3 (2.0) vs. 6.1 (1.5) U/L), and stronger LH-T feedforward synchrony (1.5 (0.3) vs. 1.9 (0.2)). Furthermore, T was positively cross-correlated with TSH (0.32 (0.21 – 0.43)), cortisol (0.26 (0.19 – 0.33)), and ACTH concentrations (0.26 (0.19 – 0.32)). Conclusions: LH concentrations were followed by T concentrations/secretion with a delay of 60 min in healthy older men, which is in line with literature. Men with a strong LH-T relationship had more favorable body composition, inflammatory markers, 24-h mean LH levels, and LH-T feedforward synchrony. In contrast, chronological age and 24-h mean T levels were not associated with the strength of the LH-T relationship. This observation could indicate that LH and health markers play a bigger role in determining the strength of LH-T cross-correlations than T and chronological age. Furthermore, we observed positive correlations between T and TSH, cortisol, and ACTH concentrations. These exploratory analyses could indicate that T and other hormones are driven by a common regulator or that there is crosstalk between these hormones.