The levels of Insulin-Like Growth Factor in Patients with Myofascial Pain Syndrome and in Healthy Controls.

BACKGROUND Insulin-like growth factor-1 (IGF-1) plays an important role in muscle maintenance and repair. The role of IGF-2 in the muscle is less clear. OBJECTIVES To compare the levels of IGF-1 and IGF-2 in acute myofascial pain syndrome (MPS) versus healthy controls and to determine whether age, sex, body mass index (BMI), region of pain, and pain intensity are associated with IGF levels. DESIGN A case-control study design included a total of 74 participants. SETTING Hospital emergency department PARTICIPANTS: Participants presenting with acute MPS (n=43) and non-MPS controls (n = 31). MAIN OUTCOME MEASURES Serum IGF-1 and IGF-2 (pg/mL) were measured in participants with MPS within 24 hours of symptom onset, and in non-MPS controls. Group and sex differences in serum IGF-1 and IGF-2 were assessed, with group and sex as factors, while controlling for age and BMI. RESULTS The mean IGF-1 levels were not significantly different between MPS and controls [88554.1 (confidence interval [CI], 79724.4-97383.7)] vs. [97911.2 (CI, 853228.7-110493.6)]. Significant differences were also not observed in IGF-1 levels between men and women with MPS nor between men and women. Mean levels of IGF-2 were significantly lower in patients with MPS than in controls [226608.9 (CI, 180057.3-273160.5)] vs. [460343.9 (CI, 387809.4-532878.2)], p<0.001). There were no significant sex differences in the levels of IGF-2 in patients with MPS. Mean IGF-2 levels pg/mL) of men and women with MPS were lower [253343.0 (CI, 179891.0-326795.0)], and [204524.2 (CI, 141176.4-267872.0)], respectively) than those of healthy men and women [428177.2 (CI, 368345.7-488008.6)], and [511274.4 (355178.6-687370.1)], respectively). Lower BMI and younger age were associated with higher levels of IGF-2. Pain intensity was associated with IGF-2, but not with IGF-1, while region of pain was not associated with either IGF-1 or IGF-2 levels. CONCLUSIONS IGF-2 levels were lower in patients with acute MPS versus healthy controls with no sex differences, while IGF-1 levels were not different among the groups. Future studies should investigate the role of IGF-2 in muscle maintenance and repair in MPS. This article is protected by copyright. All rights reserved.