Association of heterogeneity of the thyroid gland with matrix metalloproteinase-3 in rheumatoid arthritis patients with Hashimoto's thyroiditis.

Background: Hashimoto's thyroiditis (HT) is highly prevalent in patients with rheumatoid arthritis (RA). The aim is to determine their relation, focusing on matrix metalloproteinase-3 (MMP-3), a marker predicting joint destruction and RA activity.

Methods: Fifty-three consecutive RA patients were prospectively separated into two groups based on the presence or absence of HT; those with and without TPO-Ab or Tg-Ab (34.0% and 66.0%, respectively). To estimate the extent of inflammation and destruction of the thyroid gland, Heterogeneity Index (HI) was determined ultrasonographically.

Results: While the male/female ratio, TSH and HI were significantly higher in those with HT than in those without (5/13 vs. 7/28, P=0.047, mean±SE; 7.25±0.69 vs.2.52±0.30 mIU/L, P<0.001; 3.8±0.2 vs.3.2±0.2%, P=0.042, respectively), no differences existed in MMP-3. In those with HT, MMP-3 correlated negatively with FT3 (rho=-0.545, P=0.048) and positively with TPO-Ab and HI (rho=0.735, P=0.02; rho=0.769, P=0.01, respectively). Among them, HI was a significant factor associated positively with MMP-3 (r=0.883, F=31.91).

Conclusions: The present study demonstrated significant increases of HI and an association between HI and MMP-3 in RA patients with HT. These findings suggest that the inflammation and destruction of the thyroid gland might be closely related to the current activity and terminal joint destruction of RA.