Novel type of references for weight aligned for onset of puberty - using the QEPS growth model

Normalization of puberty and adult height in girls with Turner syndrome: results of the Swedish Growth Hormone trials initiating transition into adulthood

Objective

To study the impact of GH dose and age at GH start in girls with Turner syndrome (TS), aiming for normal height and age at pubertal onset (PO) and at adult height (AH). However, age at diagnosis will limit treatment possibilities.

Methods

National multicenter investigator-initiated studies (TNR 87-052-01 and TNR 88-072) in girls with TS, age 3-16 years at GH start during year 1987-1998, with AH in 2003-2011. Of the 144 prepubertal girls with TS, 132 girls were followed to AH (intention to treat), while 43 girls reduced dose or stopped treatment prematurely, making n=89 for Per Protocol population. Age at GH start was 3-9 years (young; n=79) or 9-16 years (old; n=53). Treatment given were recombinant human (rh)GH (Genotropin^® Kabi Peptide Hormones, Sweden) 33 or 67 µg/kg/day, oral ethinyl-estradiol (2/3) or transdermal 17β-estradiol (1/3), and, after age 11 years, mostly oxandrolone. Gain in height_SDS, AH_SDS, and age at PO and at AH were evaluated.

Results

At GH start, height_SDS was -2.8 (versus non-TS girls) for all subgroups and mean age for young was 5.7 years and that of old was 11.6 years. There was a clear dose-response in both young and old TS girls; the mean difference was (95%CI) 0.66 (-0.91 to -0.26) and 0.57 (-1.0 to -0.13), respectively. The prepubertal gain_SDS (1.3-2.1) was partly lost during puberty (-0.4 to -2.1). Age/height_SDS at PO ranged from 13 years/-0.42 for GH_67young to 15.2 years/-1.47 for GH_33old. At AH, GH_67old group became tallest (17.2 years; 159.9 cm; -1.27 SDS; total gain_SDS, 1.55) compared to GH_67young group being least delayed (16.1 years; 157.1 cm; -1.73 SDS; total, 1.08). The shortest was the GH_33young group (17.3 years; 153.7 cm: -2.28 SDS; total gain_SDS, 0.53), and the most delayed was the GH_33old group, (18.5 years; 156.5 cm; -1.82 SDS; total gain_SDS, 0.98).

Conclusion

For both young and old TS girls, there was a GH-dose growth response, and for the young, there was less delayed age at PO and at AH. All four groups reached an AH within normal range, despite partly losing the prepubertal gain during puberty. Depending on age at diagnosis, low age at start with higher GH dose resulted in greater prepubertal height gain, permitting estrogen to start earlier at normal age and attaining normal AH at normal age, favoring physiological treatment and possibly also bone health, hearing, uterine growth and fertility, psychosocial wellbeing during adolescence, and the transition to adulthood.

Novel type of references for BMI aligned for onset of puberty - using the QEPS growth model

OBJECTIVES

Despite inter-individual variations in pubertal timing, growth references are conventionally constructed relative to chronological age (C-age). Thus, they are based on reference populations containing a mix of prepubertal and pubertal individuals, making them of limited use for detecting abnormal growth during adolescence. Recently we developed new types of height and weight references, with growth aligned to age at onset of the pubertal growth spurt (P-age). Here, we aim to develop a corresponding reference for pubertal BMI.

METHODS

The QEPS-height and weight models were used to define a corresponding QEPS-BMI model. QEPS-BMI was modified by the same individual, constitutional weight-height-factor (WHF) as computed for QEPS-weight. QEPS-BMI functions were computed with QEPS weight and height functions fitted on longitudinal measurements from 1418 individuals (698 girls) from GrowUp₁₉₉₀Gothenburg cohort. These individual BMI functions were used to develop BMI references aligned for height at AgeP5; when 5% of specific puberty-related (P-function) height had been attained. Pubertal timing, stature at pubertal onset, and childhood BMI, were investigated in subgroups of children from the cohort GrowUp₁₉₇₄Gothenburg using the new references.

RESULTS

References (median, standard deviation score (SDS)) were generated for total BMI (QEPS-functions), for ongoing prepubertal growth (QE-function) vs C-age, and for total BMI and separated into BMI specific to puberty (P-function) and BMI gain from ongoing basic growth (QES-functions), allowing individual growth to be aligned based on P-age. Growth in basic BMI was greater than average for children categorized as tall and/or with high-BMI at puberty-start. In children categorized as short at puberty-start, P-function-related-BMI was greater than average.

CONCLUSIONS

Use of these new pubertal BMI references will make it possible for the first time to consider individual variations owing to pubertal timing when evaluating BMI. This will improve the detection of abnormal changes in body composition when used in combination with pubertal height and weight references also abnormal growth. Other benefits in the clinic will include improved growth monitoring during treatment for children who are overweight/obese or underweight. Furthermore, in research settings these new references represent a novel tool for exploring human growth.