Novel model to study the physiological effects of temporary or prolonged sex steroid deficiency in male mice.

Sex steroids are critical for skeletal development and maturation during puberty as well as for skeletal maintenance during adult life. However, the exact time during puberty when sex steroids have the highest impact as well as the ability of bone to recover from transient sex steroid deficiency is unclear. Surgical castration is a common technique to study sex steroid effects in rodents, but it is irreversible, invasive, and associated with metabolic and behavioral alterations. Here, we used a low dose (LD) or a high dose (HD) of gonadotropin-releasing hormone antagonist to either temporarily or persistently suppress sex steroid action in male mice, respectively. The LD group, a model for delayed puberty, did not show changes in linear growth or body composition, but displayed reduced trabecular bone volume during puberty, which fully caught up at adult age. In contrast, the HD group, representing complete pubertal suppression, showed a phenotype reminiscent of that observed in surgically castrated rodents. Indeed, HD animals exhibited severely impaired cortical and trabecular bone acquisition, decreased body weight and lean mass, and increased fat mass. In conclusion, we developed a rodent model of chemical castration that can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.NEW & NOTEWORTHY We developed a rodent model of chemical castration, which can be used as an alternative to surgical castration. Moreover, the transient nature of the intervention enables to study the effects of delayed puberty and reversibility of sex steroid deficiency.

Height growth in children with asthma treated with guideline-recommended dosages of fluticasone and electronically assessed adherence.

BACKGROUND AND AIMS: Inhaled corticosteroids (ICS) reduce growth during the first year of treatment, but this growth suppressing effect does not continue during further treatment. Decreasing adherence may play a role in explaining this. The aim of this study was to examine the relationship between cumulative real exposure (with objectively assessed adherence) to ICS and height growth in children with asthma. METHODS: We investigated 99 prepubertal children with asthma, 2-13 years of age, who had been using ICS in guideline-recommended dosages for ≥3 months, and continued to do so during 1-year follow-up. ICS adherence was assessed by electronic monitoring devices, allowing calculation of true cumulative exposure to ICS. We analysed the relationship between cumulative ICS dose and height growth velocity (assessed as change in height SD score) over 1 year. RESULTS: Median (IQR) adherence over 1 year was 84 (68-92) %. Mean cumulative fluticasone dose was 64.6 (SD, 27.8) mg, reflecting a daily dose of 167 (SD, 7) µg. The negative correlation between cumulative ICS dose and height growth velocity (r=-0.266; p=0.008) became non-significant after adjustment for age and sex in a multiple regression model (adjusted r=-0.188; p=0.066). CONCLUSIONS: One year of ICS treatment in guideline-recommended dosages with high adherence did not result in significant or relevant growth suppression. Unaffected growth can be maintained for at least 1 year in children with asthma during ICS treatment with high adherence.