Bone turnover markers in patients with differentiated thyroid carcinoma after levothyroxine withdrawal

Patients receiving postoperative radioiodine therapy for advanced differentiated thyroid carcinoma (DTC) are repeatedly in short-term thyroid hormone deficiency, whose bone turnover state is not fully understood.

Serum bone turnover markers (BTMs), bone specific alkaline phosphatase (BALP), type 1 procollagen N-terminal propeptide (P1NP), osteocalcin (OC), and the beta-isomerized C-terminal telopeptide of type 1 collagen (beta-CTx) were measured in 50 adult male DTC patients after 4-week suspension of levothyroxine replacement therapy and 40 matched euthyroid controls. Relationships between parameters of thyroid function (free triiodothyronine, FT3; free thyroxine, FT4; thyroid stimulating hormone, TSH) and the BTMs were studied.

The patients had significantly decreased OC (-37.6%, P<0.001) and beta-CTx (-35.5%, P<0.001) compared with the controls, showing FT3 as the independent risk factor for OC (R2=0.425, P<0.001) and beta-CTx (R2=0.124, P<0.001). Partial correlation analysis showed that only FT3 was significantly correlated with OC after controlling FT4 and TSH (r=0.362, P=0.001).

DTC patients have moderately decreased bone turnover after short-term suspension of thyroxine suppressive therapy, with serum FT3 concentration as the predominant and independent risk factor.