The hypothalamus is crucially involved in the circadian timing of the sleep-wake rhythm, yet also accommodates the most important thermoregulatory neuronal network. We have shown before that adults with pituitary insufficiency and history of chiasm compression due to a tumor with suprasellar extension fall asleep later and sleep shorter than those without such history and presumed hypothalamic involvement. To solidify the hypothesized link between vigilance and thermoregulation by the hypothalamus, we aimed to test the hypothesis that the presumed hypothalamic impairment in these patients also affects skin temperature and its association with sleep onset. In a case-control study of 50 patients (54.7±14.5 yrs of age, 30 males) with pituitary insufficiency, 33 of whom had a history of chiasm compression, ambulatory distal and proximal skin temperatures were assessed continuously for 24h. Sleep parameters were assessed via questionnaire. Group differences in mean skin temperature, calculated over the wake and sleep periods separately, and group differences in the strength of association between pre-sleep skin temperature and sleep onset latency were compared. Results showed that patients with a medical history of chiasm compression had lower proximal skin temperature during the day (34.1°C±.7°C vs. 34.6°C±.7°C, p.045). Additionally, the typical association between sleep onset latency and pre-sleep distal-to-proximal skin temperature gradient was absent in these patients (r-.01, p.96), whereas it was unimpaired in those without chiasm compression (r-.61, p.02). Thus, patients with history of chiasm compression show impaired skin temperature regulation in association with disturbed sleep. The findings support the hypothesis that a medical history of chiasm compression affects hypothalamic regulation of both vigilance and temperature, possibly by chronically affecting relevant nuclei, including the ventrolateral preoptic area and anterior hypothalamic preoptic area. (Corresponding Author: email@example.com) © Informa Healthcare USA, Inc.