ESPE Abstracts

Background: Few studies have investigated how the pubertal increase in testicular volume (TV) is related to pubertal growth spurt in a longitudinal setting. Increased TV, indicating onset of puberty in boys, mirrors the enhanced testosterone production in the testicles which also give rise to the pubertal growth spurt. The QEPS-growth model makes it possible to conduct detailed analyses of pubertal growth and separate total growth into specific pubertal (P-function) height gain and basal growth (QES-functions)^1,2.

Objective: To investigate the relationship between increase in TV in healthy boys with their pubertal growth spurt. To visualize the individual variation in the relation between TV and the attained specific pubertal height gain.

Method: The study group included 31 healthy boys, longitudinally followed during puberty with 1-4 yearly visits, including height measurements and assessments by trained paediatric endocrinologists of testicular volumes (TV), by the method of Prader³. TV during puberty were assessed in median 5 times (range 2-26). Analyses of growth patterns were done with the QEPS-growth model^1,2 and pubertal heights expressed in both cm and by QEPS-growth estimates, i.e. how many % of the specific P-function-pubertal growth that was attained at each visit. The testicular volume was related to % of the specific P-function-pubertal gain attained (P%).

Results: As expected, there was a high correlation between TV and the specific P-function-pubertal gain (>90% explained), and each boy followed his trajectory. However, the individual variation was considerable: at TV 3ml, median 6%, "P6%",(range 0.2-24%) of the specific P-function-pubertal growth was reached. Corresponding values at 4,6,8,10,12,15,20 and 25 ml TV were 14,18,35,40,58,80,95 and 98%, Table:

Mean and range of P%; of specific P-function-pubertal height gain attained at different TV; testicular volumes.

Conclusion: The specific pubertal gain in height has for the first time been analysed/visualized in relation to TV during puberty. We found a high correlation between TV and specific pubertal height gain, demonstrating the validity of the QEPS-model in this new setting. Each boy followed his trajectory, with broad inter-individual variation in TV vs P%, of the specific P-function-pubertal height gain.

References: 1.Nierop A.F.M,et.al. J.Theoretical.Biology,406(2016)143–165.

2.Holmgren A,et.al. BMC.Pediatrics,2017;Apr19;17(1):107.

3.Zachmann M,et.al. Helvetica.Paediatica.Acta,1974;29(1):61-72.