Suppressive Doses of Thyroxine Do Not Accelerate Age-Related Bone Loss in Late Postmenopausal Women

Abstract

To examine whether suppressive doses of thyroxine have any adverse effects on bone, we evaluated various bone metabolic markers (lectin-precipitated alkaline phosphatase, osteocalcin, carboxyl-terminal region of type I collagen propeptide, tartrate-resistant alkaline phosphatase, and urinary excretion of hydroxyproline and pyridinium crosslinks), incidence of vertebral deformity, total body and regional (lumbar spine and radius) bone mineral densities (BMDs), and rates of bone loss in 24 late postmenopausal (more than 5 years after menopause) women who were treated with levothyroxine (L-T4) after total thyroidectomy for differentiated carcinoma. Depending on the clinical records, including serum TSH levels measured by immunoradiometric assay, these patients were divided into two groups. One group of patients was given suppressive doses of L-T4 (TSH < 0.1 mU/L, n = 12) and the other group was given nonsuppressive doses of L-T4 (TSH > 0.1 mU/L, n = 12). There was no difference in bone metabolic markers and incidence of vertebral deformity between the groups. In patients with TSH suppression, Z-scores of BMDs calculated from age-matched healthy women (n = 179, aged 55 to 80) were nearly in the zero range of values (0.077 at total body, 0.228 at lumbar spine, and -0.117 at trabecular region of lumbar spine). The rate of bone loss in TSH-suppressed patients (-0.849 +/- 0.605%/year) was not significantly different from that of nonsuppressed patients (-0.669 +/- 0.659). These prospective and cross-sectional data suggest that long-term levothyroxine therapy using suppressive doses has no significant adverse effects on bone.

Hip bone mineral density, bone turnover and risk of fracture in patients on long-term suppressive L-thyroxine therapy for differentiated thyroid carcinoma

“…Premenopausal n ¼ patients and nonsuppressed patients (39). We found four patients in this group (7%) with one or more vertebral fractures defined as a reduction of 20% or more of the anterior, middle or posterior height.…”

Long-term treatment-related morbidity in differentiated thyroid cancer: a systematic review of the literature

“…The majority of study populations had undergone total or near TT followed by RAI and THST. In all but 6 studies,25,27–31 the control groups were comprised of healthy euthyroid-matched individuals or local reference populations. In 2 studies,28,30 the control group suffered from benign thyroid disease.…”

The effects of thyrotropin-suppressing therapy on bone metabolism in patients with well-differentiated thyroid carcinoma

“…Previous clinical studies examining the effects of LT4 therapy on bone in patients with DTC have revealed conflicting outcomes [9][10][11][12]. There are three explanations for these discrepancies.…”

“…Second, the varying duration of TSH suppression among studies might have contributed to the differences [9]. Changes in the vertebral BMD among patients with suppressed TSH during the first year following initiation of LT4 therapy were higher than in subsequent years [10,14]. Even appropriate LT4 replacement therapy without TSH suppression could lead to bone loss during the first year of treatment [15].…”