Sodium levothyroxine is not recognized as a foreign antigen; thus, allergic reactions to levothyroxine should not occur. However, an allergic reaction to the coloring agents of levothyroxine has been reported.82 In this situation, taking a noncolored tablet prevents an allergic reaction.
Thyroid hormone is known to increase osteoclastic activity.83 It is documented that patients with untreated Graves' disease will develop bone loss.84 This is because of persistently high levels of circulating thyroid hormone levels for prolonged periods. There is controversy regarding how patients who have had thyroidectomy for thyroid cancer should be managed. In general, TSH suppression with high-normal T3 and T4 levels is recommended. There are conflicting opinions about the risks and benefits when patients' serum TSH levels are chronically suppressed.85,86 Recently, Quan and associates analyzed the effect of thyroid hormone on bone mineral density in 11 studies that also describe confounding factors relevant to bone loss.87 They concluded that thyroid hormone suppression treatment does not affect bone mineral density in premenopausal women and in men. However, the effect of TSH suppression in postmenopausal women remains controversial.
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