Changes of bone mineral density in pre-menopausal women with differentiated thyroid cancer receiving L‐thyroxine suppressive therapy

ABSTRACT

Objective: We studied the effect of levothyroxine (L-T4) suppressive therapy on bone mineral density (BMD) in pre-menopausal women with total thyroidectomy and radioactive iodine (131I) ablation therapy post-operatively for differentiated thyroid cancer (DTC).

Patients and methods: We prospectively studied 26 athyroid pre-menopausal women (median age 39 years, range 28–48 years) receiving suppressive L‐T₄ therapy postoperatively for 48 months. BMD was measured by dual energy X‐ray absorptiometry (DEXA) at the femoral neck, femoral trochanter and Ward's triangle, before (basal) and during (12th and 48th month) the follow-up period. None of the women gave a medical history that could possibly affect bone metabolism. Patients were free of thyroid cancer in clinical and laboratory examinations at the time of the study. Paired t‐test was used for comparisons among BMD measurements during the suppressive therapy.

Results: There were statistically significant decreases of BMD at all measured regions during (12th and 48th month) L‐T₄ suppressive therapy. The overall decreases in BMD at the femoral neck, femoral trochanter and Ward's triangle were 7.5%, 10.9% and 3.4%, respectively, at the end of the follow-up period. The coefficient of variation (CV) of all BMD measurements was around 10%, showing a rather homogenous group of patients. Our patients had a statistically significant decrease in their body mass index (BMI) and weight at the end of the follow-up period. However, there was no significant correlation between the decrease in BMI and BMD. Patients did not experience significant adverse effects from L‐T₄ suppressive therapy during the study.

Conclusion: L‐T₄ suppressive therapy for at least 1 year in pre-menopausal women with DTC causes a reduction in BMD of the femoral neck, femoral trochanter and Ward's triangle.

Key words: :

• Bone mineral density
• Levothyroxine
• Pre-menopausal women
• Suppressive therapy