High cathepsin K levels in men with differentiated thyroid cancer on suppressive L-thyroxine therapy.
BACKGROUND
Thyroid hormone administration is associated with low bone density in some studies. The aim of the present study was to evaluate the influence L-thyroxine, in doses used to treat patients with a history of thyroid carcinoma, on serum cathepsin K and other markers of bone metabolism. Cathepsin K is thought to have a role in osteoclast mediated bone resorption.


METHODS
A group of male patients with differentiated thyroid cancer (DTC) on suppressive L-thyroxine therapy (DTC-group; n = 51; mean age 57 years; TSH < 0.1 mU/L) was selected as a model for hyperthyroidism. The results were compared to a group of healthy euthyroid men (control-group; n = 50; mean age 58 years; TSH 1.5 +/- 0.9 mU/L).


RESULTS
In the DTC-group the median value of cathepsin K was 6.9 pmol/L, in the control group 4.8 pmol/L (p = 0.0052; highly significant [h.s.]). There was a significant negative correlation of cathepsin K with age (r = -0.279, p = 0.028). The analysis of various bone associated parameters revealed an increase of serum crosslaps in the DTC-group versus euthyroid controls (p = 0.03). A significant correlation could be found for cathepsin K and osteoprotegerin (p = 0.002).


CONCLUSIONS
Cathepsin K is increased by a suppressive L-thyroxine therapy and decreases with increasing age. The increased cathepsin K levels seen in DTC-patients on suppressive L-thyroxine therapy are likely to contribute to accelerated bone degradation in these patients.
Mikosch
Peter
P
Department of Internal Medicine II, Klagenfurt State Hospital, Klagenfurt, Austria. peter.mikosch@tele2.at
Kerschan-Schindl
Katharina
K
Woloszczuk
Wolfgang
W
Stettner
Haro
H
Kudlacek
Stefan
S
Kresnik
Ewald
E
Gallowitsch
Hans J
HJ
Lind
Peter
P
Pietschmann
Peter
P
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000097:blood; D001842:Bone and Bones / Q000378:metabolism; D002291:Carcinoma, Papillary / Q000097:blood* / Q000601:surgery; D016022:Case-Control Studies; D056657:Cathepsin K; D002403:Cathepsins / Q000097:blood*; D003094:Collagen / Q000097:blood; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D013964:Thyroid Neoplasms / Q000097:blood* / Q000601:surgery; D013974:Thyroxine / Q000494:pharmacology*
D015415:Biomarkers; D053244:Osteoprotegerin; D010446:Peptide Fragments; C110762:glutamyl-lysyl-alanyl-histidyl-aspartyl-glycyl-glycyl-arginine; D003094:Collagen; D002403:Cathepsins; C534130:CTSK protein, human; D056657:Cathepsin K; D013974:Thyroxine