PROLACTIN SECRETION DURING SLEEP IN OBSTRUCTIVE SLEEP-APNEA PATIENTS

Plasma prolactin (PRL) concentration exhibits a sleep-dependent patter n, with highest levels during sleep and lowest levels during the wakin g period. The syndrome of obstructive sleep apnoea (OSA) is associated with severe hypoxaemia and chronic sleep fragmentation, both of which could affect the sleep-entrained PRL rhythm. Treatment with nasal con tinuous positive airway pressure (CPAP) immediately restores a normal sleep structure by successful abolition of the apnoeas. In the present study, seven OSA patients underwent two night studies, once when no t reatment was given and once during the first night of CPAP treatment. Sleep was recorded polygraphically in all experiments. Plasma PRL was measured at 10 min intervals and secretory rates were calculated by a deconvolution procedure. CPAP treatment greatly reduced hypoxaemia and improved sleep quality. The secretory pulse amplitude and the total a mount of PRL secreted during the night remained constant regardless of whether patients were treated or not. The only difference found was a lower pulse frequency in untreated OSA patients as compared to treate d patients, which may be attributed either to hypoxaemia or to sleep d isturbance or to the combined action of both. Treatment may be conside red to normalize PRL release by restoring pulse frequency to values si milar to those observed for normal subjects.