[Somatotropin secretion during sleep in 60 cases of growth retardation in children].

A study of nocturnal somatotropic secretion with sleep polygraphic recording was performed in 60 children, aged 1 to 18 years and presenting with growth retardation greater than or equal to -2SD. GH secretion was analysed according to the peak value, the number of peaks greater than 5 ng/ml and the integrated concentration (surface under the curve divided by the duration of the test). The children were studied in four groups according to the responses to pharmacologic stimulation tests: a normal group (n = 7), a group with complete somatotropic deficiency (n = 4), a group with partial somatotropic deficiency (n = 39) and a group with dissociated responses (n = 12). Results are concordant between sleep secretion and pharmacologic tests in the first two groups. On the contrary, in the two last, the study of the sleep secretion allows to differentiate children with hyposecretion ("true partial deficiencies") from children with normal secretion ("false partial deficiencies") or abnormal responders). In other respects, correlations between LH maximum peak and stages of sleep are analysed. The maximum peak was observed in only 33.9% of cases during stage IV, 21.5% of cases during stages I, II, III, in 19.6% of cases during wakefulness and in 25% of cases during paradoxical stage. The maximum peak was observed in only 48% of cases during the first cycle of sleep and in 52% of cases during the other cycles. These results show that the correlation between maximum peak, stage IV and first cycle of sleep is not absolute.