No evidence for extraocular light induced phase shifting of human melatonin, cortisol and thyrotropin rhythms.
Neuroreport
; 11(4): 713-7, 2000 Mar 20.
Article
in En
| MEDLINE
| ID: mdl-10757506
ABSTRACT
The view that light affects the mammalian circadian clock only through the eyes was recently challenged by a study in which the phases of human circadian rhythms were shifted by extraocular light exposure. This finding has not been confirmed, however. We studied the effects of light exposure (3 h, broad spectrum fluorescent white light, 13000 lux) on abdomen and chest on the circadian rhythms of serum melatonin, cortisol and thyrotropin in six subjects. The protocol consisted of two 3-day sessions in a dimly lit (< 10 lux) experimental unit. In both sessions hourly serum samples were collected for hormone analysis on days 1 and 3. The skin light exposure was delivered on day 2 from 22.00 to 01.00h in one of the two sessions in a randomized order. In both sessions all three rhythms tended to delay, presumably due to the endogenous circadian cycle length being slightly longer than 24 h. However, the phase shifts did not differ significantly between the sessions. Thus, the present study does not support the existence of extraocular photic regulation of the circadian rhythms in humans.
Search on Google
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Hydrocortisone
/
Thyrotropin
/
Circadian Rhythm
/
Light
/
Melatonin
Type of study:
Clinical_trials
Limits:
Adolescent
/
Adult
/
Female
/
Humans
/
Male
Language:
En
Journal:
Neuroreport
Journal subject:
NEUROLOGIA
Year:
2000
Document type:
Article
Affiliation country:
Finland