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GH deficiency not observed in adults with Prader-Willi syndrome treated in childhood
A cohort of young adults with Prader-Willi syndrome treated with growth hormone therapy as children did not meet criteria for adult GH deficiency after accounting for BMI; however, borderline-low GH levels continued to persist for some, according to findings published in Clinical Endocrinology.
“It was generally believed that young adults with [Prader - Willi syndrome] would have GH [ deficiency] and could continue GH treatment after attainment of adult height,” Stephany H. Donze, MD, of the Dutch Research Foundation and the department of pediatrics, subdivision of endocrinology at Erasmus University Medical Center-Sophia Children’s Hospital in the Netherlands, and colleagues wrote. “However, completely unexpected, none of the 60 young adults fulfilled the current consensus criteria for the diagnosis of adult GH [deficiency].”
In a cross-sectional study, Donze and colleagues analyzed data from 60 young adults with Prader-Willi syndrome who received at least 2 years of GH treatment during childhood and attained adult height; all participants were followed at the Dutch PWS Reference Centre (33 women; median age, 18 years). Participants underwent a standard GH stimulation test with GH-releasing hormone (GHRH) and arginine to measure levels of GH, insulin-like growth factor I and IGF binding protein-3. Body composition was assessed via DXA. Adult GH deficiency was defined as a GH peak level of less than 9 µg/L after testing combined with a serum IGF-I standard deviation score (SDS) level of less than –2, adjusted for age and sex. Researchers used Pearson’s correlation coefficients to assess relationships between IGF-I and GH peak and anthropometric measurements and body composition variables.
Within the cohort, GH treatment in childhood was initiated at a median age of 7 years. After adult GH stimulation testing, median GH peak was 17.8 µg/L, median serum IGF-I was –0.4 SDS and IGF binding protein-3 was 1.6 SDS.
Researchers found that none of the participants fulfilled the criteria of adult GH deficiency. Serum IGF-I was less than –2 SDS in two patients, and IGF binding protein-3 was within the normal range in all but one participant. Nine participants (15%) had a peak GH level of less than 9 µg/L during GH stimulation testing; however, no participants had an IGF-I level less than –2 SDS. When using BMI-dependent criteria, nine participants had a GH peak below the cutoff, according to researchers.
Researchers found that higher BMI SDS was associated with lower GH peak (P < .01), as was higher fat mass percentage (P < .01); however, GH peak was not correlated with age or waist-to-hip ratio or with IGF-I SDS.
“Against expectations, our data show that none of the patients had adult GH [deficiency] according to the consensus criteria, also when BMI was taken into account,” the researchers wrote. “Results were variable, with some patients having a low serum IGF-I and normal GH peak, and others a normal serum IGF-I and low GH peak.”
Researchers noted that the data are in line with that of patients without Prader-Willi syndrome who were diagnosed with idiopathic, childhood-onset GH deficiency who have a normal response to GH stimulation testing as adults.
“The reasons why are unknown, but may include a variable GH response to stimulation, GH [deficiency] being a transient condition or GH [deficiency] being partial, preventing normal growth during childhood but not causing symptoms in adulthood,” the researchers wrote. “We can, however, not exclude that GH treatment stimulates GH secretory cells in the pituitary, and that this GH effect persists, even after GH treatment is discontinued.” – by Regina Schaffer
Disclosure: One of the authors reports he has received an independent research grant from Pfizer.