Bone mineral density and bone turnover markers in patients on long-term suppressive levothyroxine therapy for differentiated thyroid cancer.
OBJECTIVE
Current management for patients with differentiated thyroid cancer includes near total thyroidectomy and radioactive iodine therapy followed by administration of supraphysiological doses of levothyroxine (L-T4). Although hyperthyroidism is a well known risk factor for osteoporosis, the effects of L-T4 treatment on bone mineral density (BMD) in patients with thyroid cancer do not appear to be as significant as with endogenous hyperthyroidism. In this study, we evaluated the impact of long-term suppressive therapy with L-T4 on BMD and bone turn over markers in Korean female patients receiving L-T4 suppressive therapy.


METHODS
We enrolled 94 female subjects (mean age, 50.84 ± 11.43 years) receiving L-T4 after total or near total thyroidectomy and radioactive iodine therapy for thyroid cancer (mean follow-up period, 12.17 ± 4.27 years). The subjects were divided into three groups by thyroid stimulating hormone (TSH) level (group 1 with TSH level ≤0.001 µIU/mL, group 2 with TSH level between 0.001 and 0.17 µIU/mL, group 3 with TSH level >0.17 µIU/mL) and four groups by quartile of free T4 level. L-T4 dosage, BMD (examined by dual-energy x-ray absorptiometry), and bone turnover markers were evaluated according to TSH and free T4 levels.


RESULTS
No significant decrease was detected in BMD or bone turnover markers according to TSH level or free T4 level. Also, the prevalence of osteoporosis and osteopenia was not different among groups.


CONCLUSIONS
Long-term L-T4 suppressive therapy after thyroid cancer management did not affect bone density or increase the prevalence of osteoporosis even though TSH levels were supraphysiologically suppressed.
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
Mi Young
MY
Lee
Department of Surgery, Yonsei University Wonju College of Medicine, Wonju, Korea.
Jae Hyun
JH
Park
Department of Surgery, Yonsei University Wonju College of Medicine, Wonju, Korea.
Keum Seok
KS
Bae
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
Yong Gwan
YG
Jee
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
An Na
AN
Ko
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
Yong Jea
YJ
Han
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
Jang Yel
JY
Shin
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
Jung Soo
JS
Lim
Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea. ; Institute of Life-Long Health, Yonsei University Wonju College of Medicine, Wonju, Korea.
Choon Hee
CH
Chung
Department of Surgery, Yonsei University Wonju College of Medicine, Wonju, Korea.
Seong Joon
SJ
Kang
Bone mineral density; Levothyroxine; Osteopenia; Osteoporosis; Thyroid neplasms