medwireNews: Growth hormone (GH) therapy has a greater impact on the metabolic outcomes of girls than boys, research suggests.

This may indicate that girls with GH deficiency (GHD) should be more closely monitored during GH treatment, with the aim of modifying their lifestyles to counteract the metabolic changes, say Carla Giordano and co-researchers, from the University of Palermo in Italy.

However, they stress that “studies with longer follow-up and a larger cohort of patients are required to confirm these preliminary results” and to establish whether closer monitoring or altering GH doses is the best approach.

There were 44 girls with GHD (peak stimulated GH <8 μg/L) in the study and 61 boys. During 24 months of treatment, the height standard deviation score (SDS) of all patients improved from an average of –2.3 to –1.4. However, average fasting glucose increased from 4.1 to 4.5 mmol/L and fasting insulin rose from 3.8 to 8.6 µU/mL. In addition, insulin resistance significantly increased and insulin sensitivity conversely declined, and the oral disposition index, which reflects the ability of beta cells to compensate for insulin resistance, also decreased.

These changes occurred in both sexes, and are consistent with most previous studies, say the researchers. They stress that fasting glucose and glycated haemoglobin levels remained within the normal range at all times.

But the team also found that the declines in insulin sensitivity and in the oral disposition index were significantly greater in girls than boys. They suggest this may be due to a greater increase in fat mass in the girls; BMI SDS increased from –0.8 to –0.6 in boys and from –0.6 to –0.2 in girls, with the difference between the two being statistically significant. Waist circumference increased from 62 to 64 cm in boys and from 62 to 67 cm in girls, a difference that bordered on statistical significance.

The  increases in insulin resistance are unlikely to have been mediated by insulin-like growth factor (IGF)-1 levels, “which were always within the normal range during the observational period and similar in males and female[s]”, say Giordano and team, adding that the change in IGF-1 levels was similar for both sexes, and they also received similar GH doses, starting at 0.025 mg/kg per day and increasing to 0.032 mg/kg per day by 24 months. Doses were not individualised.

Therefore, the larger increases in BMI and waist circumference in girls versus boys “suggests that adiposity might be a mediator of the different metabolic effects of GH [therapy]”, they conclude in Endocrine Connections.

Eleanor McDermid

Endocr Connect 2018; Advance online publication

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