There have been few studies on acute changes of bone metabolism in humans by
thyroid hormone. This study aimed to examine the effects of
triiodothyronine on
serum markers of bone and
mineral metabolism during a 7-d course of daily 75 microg
therapy in 14 normal volunteers by drawing blood on 1, 2, 3, 5, and 7 d of
therapy. Serum
calcium concentrations did not significantly change during the course of
therapy, while serum
phosphorus concentrations were significantly (p < 0.05) decreased from 3.21 +/- 0.43 mg/dL (mean +/- SD) to 2.85 +/- 0.46 mg/dL on the 7th d. Serum PTH concentrations were significantly decreased from 339 +/- 116 pg/mL to 316 +/- 29 pg/mL. Serum concentrations of
alkali-
phosphatase and bone-specific
alkali-
phosphatase were not significantly changed, but serum
osteocalcin concentrations were significantly increased from 5.71 +/- 1.98 mg/dL to 6.73 +/- 2.24 mg/dL. Serum carboxy-terminal propeptide of
type I collagen concentrations were significantly decreased from 137.8 +/- 33.7 microg/L to 119.2 +/- 33.6 microg/L. Serum
pyridinoline cross-linked telopeptide domain of
type I collagen concentrations, a
bone resorption marker, were significantly increased from 3.40 +/- 0.77 to 3.87 +/- 1.05 microg/L, and such significant increase was obtained from the 3rd day. The results indicate that some of bone and
mineral markers change rapidly in response to
triiodothyronine-induced acute
thyrotoxicosis, but the manner of change is not the same as that of chronic
thyrotoxicosis.