Osteoporosis and thyrotropin-suppressive therapy: reduced effectiveness of alendronate.
BACKGROUND
Many reports of the effect of exogenous thyroxine therapy on bone mineral density (BMD) show a relationship between excess thyroid hormone administration and osteoporosis. The aim of this study was to evaluate the effect of antibone resorptive agents, in particular alendronate (ALN) on BMD in postmenopausal osteoporotic women with thyroid carcinoma who were receiving long-term thyrotropin (TSH)-suppressive therapy with thyroxine.


METHODS
Seventy-four postmenopausal women with low BMD (T-score < or =-2.5) and differentiated thyroid carcinoma on long-term TSH-suppressive therapy (TSH > or =0.05 and < or =0.1 microU/mL) for about 3-9 years were selected for the study. The patients were divided into three groups according to the length of levothyroxine (LT(4)) treatment prior to the beginning of the study: group A (TSH-suppressive therapy for about 3 years), group B (for about 6 years), and group C (for about 9 years). These patients were compared with 74 matched women not taking LT(4). All patients and controls were treated with bisphosphonates, calcium, and vitamin D for 2 years and evaluated.


RESULTS
After 24 months of treatment group A showed a 7.8% increase in lumbar BMD; group B, a 4.6% increase; and group C, a 0.86% increase. In the control group BMD increased 8.2%. A significant difference was found in both lumbar and femoral BMD increase among the three groups: group C had a lower BMD increase than group A (p < 0.001) and B (p < 0.001).


CONCLUSIONS
In postmenopausal women who were receiving adequate amounts of calcium and vitamin D in their diet ALN was less effective for those who were also receiving TSH-suppressive doses of LT(4) for either 6 or 9 years. The positive effect of ALN on BMD was less for longer periods of LT(4) treatment. It seems likely that other bisphosphonates would also be less effective in increasing BMD in postmenopausal women receiving TSH-suppressing doses of LT(4).
Department of Endocrinology and Molecular and Clinical Oncology, University of Naples Federico II, Naples, Italy.
Annalisa
A
Panico
Gelsy Arianna
GA
Lupoli
Francesco
F
Fonderico
Francesca
F
Marciello
Addolorata
A
Martinelli
Roberta
R
Assante
Giovanni
G
Lupoli
D000328:Adult; D019386:Alendronate / Q000627:therapeutic use*; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects*; D015519:Bone Density / Q000187:drug effects*; D050071:Bone Density Conservation Agents / Q000627:therapeutic use*; D002118:Calcium / Q000627:therapeutic use; D002277:Carcinoma / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D016022:Case-Control Studies; D019587:Dietary Supplements; D004347:Drug Interactions; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000187:drug effects; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000187:drug effects; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000000981:diagnostic imaging / Q000188:drug therapy*; D011859:Radiography; D013964:Thyroid Neoplasms / Q000150:complications / Q000188:drug therapy* / Q000473:pathology; D013974:Thyroxine / Q000009:adverse effects*; D013997:Time Factors; D016896:Treatment Outcome; D014807:Vitamin D / Q000627:therapeutic use
D018931:Antineoplastic Agents, Hormonal; D050071:Bone Density Conservation Agents; D014807:Vitamin D; D013974:Thyroxine; D002118:Calcium; D019386:Alendronate