Endocrine Abstracts

Introduction: TSH seems to play direct role in bone metabolism. TSH receptors are expressed on osteoblasts and osteoclast precursors. Osteocalcin (OC) is well known marker of bone formation, whereas collagen type I crosslinked C-telopeptide I (CTX) is marker of bone resorption. Sclerostin is a protein, recently found to inhibit bone formation, while parathormone (PTH) inhibits sclerostin production. The aim of the study was to estimate sclerostin, OC, CTX and PTH levels after recombinant human TSH (rhTSH) injections in patients treated for thyroid cancer.

Patients and methods: The analysis included 33 postmenopausal women in age from 43 to 73 years (mean age 52±10.7 years, mean±S.D.) who underwent surgery for papillary thyroid carcinoma (PTC) and were treated with suppressive doses of L-thyroxine, undergoing stimulation with exogenous rhTSH (Thyrogen Genzyme) during routine evaluation for cancer remnants. Serum sclerostin, OC, CTX and PTH concentrations were measured. A blood sample was drawn from each patient at baseline and 5 days after rhTSH administration.

Results: A significant rise in CTX in serum after TSH injection was observed (P=0.013).

Serum sclerostin and osteocalcin levels did not change significantly over the time (P>0.05).

Serum PTH level started to rise along with TSH but a significant increase of PTH was only reached on day 5. There was no significant correlation between TSH concentration and the various parameters measured.

Conclusions: The acute TSH administration results in an increase of CTX but does not affect sclerostin and osteocalcin levels.