Thyroid hormones in systemic lupus erythematosus: the catalyst for disease progression?

Objective: The study aimed to investigate the impact of varying thyroid function statuses on clinical and laboratory indicators in patients with systemic lupus erythematosus (SLE).

Methods: A retrospective analysis was conducted on 258 patients with SLE, who were stratified according to thyroid function, renal involvement, and disease activity. The predictive value of thyroid hormones was evaluated using a receiver operating characteristic (ROC) curve.

Result: Among the 258 patients with SLE, 141 were classified as the normal group, while 117 exhibited thyroid hormone abnormalities, categorized into hypothyroidism (N=112) and hyperthyroidism (N=5) groups. Serum levels of FT3 and FT4 positively correlate with total protein and albumin, while negatively correlating with the SLE Disease Activity Index 2K (SLEDAI-2K) and 24-hour urinary protein (24hUP) (P<0.05). Compared to individuals without renal involvement, those with renal involvement exhibited lower levels of FT3 and FT4 (3.35±0.99 vs. 4.07±2.22, 12.92±3.14 vs. 14.63±3.39, P=0.001), along with elevated thyroid-stimulating hormone (TSH) levels (7.08±14.40 vs. 5.28±12.48, P=0.343). The subgroups in euthyroid (n=86) and hypothyroid (n=93) of SLE patients with renal involvement exhibited different characteristics (P<0.05). The levels of FT3 gradually decreased with increase of disease activity. The areas under the ROC curve of FT3, FT4, TSH and their combination were 0.651, 0.654, 0.643, 0.669, respectively (P<0.05).

Conclusions: The correlation between thyroid function and the severity of SLE is significant, SLE patients with hypothyroidism exhibit more pronounced disease manifestations and an elevated risk of organ damage. SLE patients with low levels of FT3 and FT4 are prone to progressing to nephritis.