Recent research suggests a potential link between levothyroxine, a widely prescribed thyroid medication for older Americans, and bone loss.

The study involved 81 euthyroid levothyroxine users and 364 non-users, with participants having a median age of 73 and followed over a period of 6.3 years.

Levothyroxine, also known as Eltroxin and sold under brand names like Synthroid, is a synthetic hormone used to treat hypothyroidism, a condition where the thyroid gland fails to produce enough thyroxine, leading to symptoms such as fatigue and weight gain.

While an underactive thyroid is not a direct risk factor for osteoporosis, prolonged high levels of thyroid hormones can contribute to low bone density and increase the risk of osteoporosis.

Excess thyroid hormone may disrupt the balance of bone tissue formation and loss, potentially leading to osteoporosis, although further research is necessary to confirm this connection.

Osteoporosis, which affects around 10 million people aged 50 and older, significantly raises the risk of debilitating fractures, particularly hip fractures, which can lead to mobility loss and increased mortality in older adults.

In the UK, osteoporosis impacts 3.5 million individuals and is often referred to as a 'silent disease' due to the absence of symptoms until fractures occur.

A study from Yale School of Medicine in 2023 indicated that up to 90% of levothyroxine prescriptions might be unnecessary, highlighting the need for more judicious prescribing practices.

Improper dosages of levothyroxine can adversely affect various bodily functions, including bone metabolism and cardiovascular health.

Dr. Jennifer Mammen, a co-author of the study, advises adults taking levothyroxine to consult healthcare providers for regular monitoring of thyroid function tests and to weigh the risk-benefit ratio of their treatment.

The findings from this study were presented at the Radiological Society of North America's annual meeting in Chicago on November 24, 2024.

Normal thyroid-stimulating hormone (TSH) levels range from 0.4 to 5.0 microunits per milliliter, with excess TSH associated with a higher risk of bone fractures.