Serum Catestatin Levels and Their Association with Pain Severity in Fibromyalgia Syndrome: A Cross-Sectional Case–Control Study

Background: Catestatin (CST) is a neuropeptide involved in autonomic regulation, inflammation, and immune responses. This study aimed to compare serum CST levels between patients with fibromyalgia syndrome (FMS) and healthy controls and to examine their associations with pain severity, disease impact, and fibromyalgia-specific quality of life. Methods: Forty women with FMS and 40 healthy women were included. Serum CST levels were measured by enzyme-linked immunosorbent assay. Pain severity, disease impact, and quality of life were assessed using the Visual Analog Scale (VAS), Fibromyalgia Impact Questionnaire (FIQ), and Fibromyalgia Quality of Life Scale (FM-QoLS), respectively. Results: No statistically significant difference in serum CST levels was detected between women with FMS and healthy women in this sample (p = 0.111). CST was inversely correlated with daytime (ρ = −0.510, p = 0.001) and nighttime pain (ρ = −0.364, p = 0.021); after correction for multiple comparisons, only the association with daytime pain remained significant. In multivariable analyses, lower CST levels remained associated with greater daytime pain severity after adjustment for age, Body Mass Index, and symptom duration; an inverse association was also observed for nighttime pain, although findings for nighttime pain were less consistent across analyses. CST was not significantly associated with symptom duration, FIQ, or FM-QoLS scores. Conclusions: Serum CST levels did not differ significantly between women with FMS and healthy women in this sample. Within the FMS group, lower CST levels were associated with greater pain severity, with the most consistent association observed for daytime pain. These findings should be considered exploratory and hypothesis-generating and do not establish CST as a diagnostic, prognostic, or clinically useful biomarker for FMS. Further studies in larger and more diverse populations are needed to confirm these findings and determine their clinical relevance.