NREM sleep architecture and relation to GH/IGF-1 axis in Laron syndrome.

Background: Laron syndrome (LS), known as growth hormone (GH) receptor deficiency, is a rare form of inherited GH resistance. Sleep disorders were described as a common feature of adult LS patients, while no data are available in children. Bi-directional interactions between human sleep and the somatotropic system were previously described, mainly between slow wave sleep and the nocturnal GH surge.

Objective: To analyze the sleep macro- and microstructure in LS and to evaluate the influence of substitutive insulin-like growth factor 1 (IGF-1) therapy on it.

Methods: Two young LS females underwent polysomnography; the first study was performed during IGF-1 therapy, the second one after a 3-month wash-out period.

Results: In both patients, the sleep macrostructure showed that time in bed, sleep period time, total sleep time, sleep efficiency and rapid eye movement (REM) percentage were all increased during wash-out. The sleep microstructure (cyclic alternating pattern: CAP) showed significantly higher EEG slow oscillations (A1%) in NREM sleep, both during IGF-1 therapy and wash-out.

Conclusions: Sleep macrostructure in LS children is slightly affected by substitutive IGF-1 therapy. Sleep microstructure shows an increase of A1%, probably related to abnormally high hypothalamic GHRH secretion, due to GH insensitivity.