Circadian variation in neuroendocrine response to L-dopa in patients with restless legs syndrome.
OBJECTIVE
To investigate circadian changes in dopaminergic function by means of a neuroendocrine challenge (growth hormone and prolactin responses to an acute oral administration of L-dopa) in patients with idiopathic restless legs syndrome (RLS) and controls.


METHODS
Randomized administration of the L-dopa neuroendocrine challenge.


METHODS
Sleep disorders laboratory at a 500-bed academic hospital.


METHODS
Twelve patients diagnosed with idiopathic RLS and 12 age- and sex-matched healthy controls.


METHODS
Following a comprehensive evaluation that included nocturnal polysomnographic study, all participants underwent the L-dopa neuroendocrine challenge on 2 occasions (11 am and 11 pm). Subjects were previously randomly assigned to the time of first challenge (11 am or 11 pm). On each occasion, subjects took 200 mg of L-dopa (plus 50 mg carbidopa) by mouth. Blood was drawn 20 minutes and 5 minutes before administration of the drug, as well as 15, 30, 45, 60, 75, 90, 102, and 120 minutes after administration.


RESULTS
Prechallenge levels of plasma values of growth hormone or prolactin did not differ in the 2 subject groups. Following only the nighttime administration of L-dopa, RLS patients manifested a more pronounced inhibition of prolactin release and an increase in growth hormone secretion. Prolactin plasma levels were significantly correlated to the periodic limb movement index on the polysomnogram.


CONCLUSIONS
These findings may reflect enhanced circadian variations in dopaminergic function and support an increased sensitivity at night of dopamine receptors in patients with RLS.
Garcia-Borreguero
Diego
D
Department of Neurology, Fundación Jiménez Díaz, Madrid, Spain. dgarciaborreguero@fjd.es
Larrosa
Oscar
O
Granizo
Juan José
JJ
de la Llave
Yolanda
Y
Hening
Wayne A
WA
D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D002940:Circadian Rhythm / Q000502:physiology*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011388:Prolactin / Q000378:metabolism; D012148:Restless Legs Syndrome / Q000175:diagnosis / Q000188:drug therapy*; D015899:Tomography, Emission-Computed, Single-Photon
D000978:Antiparkinson Agents; D007980:Levodopa; D011388:Prolactin; D006854:Hydrocortisone