February 1992

Borderline-Low Serum Thyrotropin Level Is Correlated With Increased Fasting Urinary Hydroxyproline Excretion

Author Affiliations

From the Bone and Mineral Division (Drs Krakauer and Kleerekoper) and Division of Endocrinology and Metabolism (Dr Krakauer), Henry Ford Hospital, Detroit, Mich.

Arch Intern Med. 1992;152(2):360-364. doi:10.1001/archinte.1992.00400140104023

• Background. —  Recent studies suggest that even mildly supraphysiologic thyroid hormonal status accelerates bone loss. In hyperthyroidism, increased bone resorption is the predominant mechanism for bone loss. We postulated that the changes in thyroid hormone status as reflected by lownormal and minimally subnormal serum thyrotropin level would have an effect on bone turnover and could be detected by a simple, noninvasive marker of bone resorption, fasting urinary total hydroxyproline-cretinine excretion (THP/Cr).

Methods.—  We retrospectively identified ambulatory patients with a restricted range of diagnoses who had had measurements of thyrotropin and THP/Cr performed within ±21 days.

Results.—  Of the 86 patients, 47 had thyrotropin levels greater than 1.0 mU/L. In these patients, no correlation was evident for thyrotropin and THP/Cr. Of the other 39 patients, 11 had suppressed thyrotropin levels (<0.1 mU/L) and showed clearly elevated values for THP/Cr, as expected from previous studies of hyperthyroidism. For 28 patients with thyrotropin in the borderline and low-normal range of 0.1 to 1.0 mU/L, a significant negative correlation with THP/Cr was found. The THP/Cr was positively correlated with serum alkaline phosphatase level, as expected with increased bone turnover.

Conclusions.—  These results add further support to the hypothesis that even a minimal excess of thyroid hormones increases bone turnover and may contribute to accelerated bone loss.(Arch Intern Med. 1992;152:360-364)