title: Circadian variations of serum myoglobin levels in normal subjects and patients with polymyositis.
abstract: Circadian variations in myoglobin levels were determined in 18 normal volunteers and in 10 patients with active polymyositis. In all the controls and in 9 of the 10 patients, serum myoglobin concentrations were highest at 9 am, fell significantly during the day to reach a nadir between 6 and 12 pm, remained constant until midnight, and then rose again at 3 am. The percent differences between the highest and lowest values ranged from 21-66%. This pattern was observed in both untreated patients and patients receiving 6-methyl-prednisolone, which was given either in a single dose at 8 am or in divided doses (8 am and 8 pm). These data demonstrate that the time of sample collection must be taken into account when myoglobin levels are used as a marker of muscle damage.
mesh_terms: D000328:Adult; D000368:Aged; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009211:Myoglobin / Q000097:blood*; D009220:Myositis / Q000097:blood*; D012737:Sex Factors
chemical_list: D009211:Myoglobin