The reviewers also pointed out that for future studies, evaluating bone mineral density alone doubtful value, but instead suggest that bone architecture and strength must be taken into account. As they state, The preferred clinically relevant outcome should rather be the prevalence or incidence of bone fracture to reveal the causal relation between levothyroxine exposure and bone.
What Does this Mean for Patients?
First, what this means is that your doctor cannot assert that taking thyroid hormone replacement causes osteoporosis or levothyroxine will reduce bone density. Its simply not proven, and in fact, the majority of the research actually contradicts this statement. This is often a reason physicians refuse to treat borderline or subclinically hypothyroid patients. They argue that the risk of osteoporosis outweighs the need for or benefits of treatment. As this research shows, this is not supported scientifically.
Second, this concern over osteoporosis is also a reason physicians refuse to slightly increase the dosage of thyroid hormone replacement when patients feel their dose is insufficient. Again, these physicians argue that the risk of osteoporosis outweighs the need for or benefits of treatment. Since the research does not support this conclusion either, again, its an issue where patients may need to assertively insist on better treatment.
Everyone with a history of hyperthyroidism, a family history of osteoporosis, and all postmenopausal women, however, should periodically be screened for risk factors of osteoporosis, including bone densitometry testing if warranted. Those who show evidence of loss of bone density should receive counseling on diet and exercise as well as receive prescriptions of osteotherapeutics when deemed necessary.
Source: Schneider R, Reiners C. The effect of levothyroxine therapy on bone mineral density: a systematic review of the literature. Exp Clin Endocrinol Diabetes. 2003 Dec;111(8):455-70