OVERNIGHT GROWTH-HORMONE SECRETION IN ACHONDROPLASIA - DECONVOLUTION ANALYSIS, CORRELATION WITH SLEEP STATE, AND CHANGES AFTER TREATMENT OFOBSTRUCTIVE SLEEP-APNEA

The normal profile for overnight GH secretion in achondroplasia has no t been previously studied. Factors that have been shown to influence G H secretion include age, obesity, sleep stat, and the presence of obst ructive sleep apnea (OSA). We assessed GH levels in a group of subject s with achondroplasia, during overnight polysomnography. Nineteen subj ects with achondroplasia were studied at 11.3 y of age (median 6.7, ra nge 1.8-30.9). Levels of GH were measured using time-resolved immunofl uorometric assay (DELFIA, Pharmacia Biotech Inc.) and analyzed by a de convolution method. Five subjects were restudied after treatment for O SA. Secretion rates of GH were greater in slow wave (SWS) and rapid ey e movement (REM) sleep than in stage one and two (SI-II = light non-RE M) sleep (p < 0.01). Total overnight GH secretion decreased with incre asing age (r(2) = 0.22 p < 0.04). Neither the frequency of arousals, f requency of sleep state transitions nor the severity of OSA correlated with measures of GH secretion. Levels of IGF-I correlated independent ly with age, body weight (percent ideal), and GH secretion rate (r(2) = 0.76, p < 0.001). In a group of five subjects treated for OSA, impro ved respiratory distress index and reduced sleep state transitions wer e not associated with significant changes in GH secretion rate by slee p stage: SWS [from 0.62 +/- 0.28 mIU/L/min to 1.02 +/- 0.25 mIU/L/min (NS)] and SI-II sleep [from 0.26 +/- 0.07 mIU/L/min to 0.60 +/- 0.16 m IU/L/min (NS)]. However, in those five subjects, a GH secretion peak d uring the first 2 h of <(S)over barWS> was initially absent, appearing only after treatment of OSA (1.09 +/- 0.38 mIU/L/min) compared with ( 2.40 +/- 0.59 mIU/L/min (p - 0.01)). A profile of overnight GH secreti on is presented for subjects with achondroplasia.