In the United States, levothyroxine is a commonly prescribed medication, especially for elderly patients, because aging can be linked to decreased thyroid function. However, because of the potential for side effects, there are still concerns about how it should be prescribed. The use of levothyroxine in individuals with normal hormone ranges may eventually result in decreased bone mass and density in older adults, according to a recent abstract presented at the annual meeting of the Radiological Society of North America.

A small cohort study found that older adults with normal thyroid levels who take levothyroxine, a medication used to treat hypothyroidism, may have decreased bone mass and density. Over a 6-year follow-up period, researchers from Johns Hopkins University School of Medicine in Baltimore, Maryland, demonstrated that adults over 65 who received levothyroxine experienced a decrease in both total body bone mass and density. On November 25, 2024, they presented the findings at the Radiological Society of North America’s Annual Meeting. A peer-reviewed publication has not yet published these findings.

The findings came from a small study with 81 participants taking levothyroxine and having normal thyrotropin levels, which are used to show thyroid function. Levothyroxine is one of the most often prescribed medications in the US, especially for older adults, according to the study’s authors. Not involved in this study was Sean Ormond, MD, of Atlas Pain Specialists, who holds dual board certifications in anesthesiology and interventional pain management.

Since thyroid issues are more likely to occur as we age, levothyroxine is a very common medication. Older adults are more likely to have hypothyroidism, a condition in which the thyroid slows down and produces insufficient hormones to maintain bodily functions. When thyroid function is compromised, people frequently experience fatigue, weight gain, cold sensitivity, or even depression. Because these symptoms can make life difficult, doctors frequently recommend levothyroxine to help people feel better by restoring hormone levels. In situations where untreated thyroid problems could endanger the heart or other organs, it’s particularly crucial, he added.

Why is the thyroid gland important?
The thyroid, which is located in the neck, is in charge of making hormones that affect metabolism, children’s growth and development, temperature regulation, and the operation of the heart and digestive system. The pituitary gland, another hormone-producing organ in the head, produces thyroid stimulating hormone (TSH). T3 and T4 are then produced by the thyroid as a result, and they are involved in the previously mentioned processes. Fatigue, weight gain, cold intolerance, dry, flaky skin, hair loss, and difficulty concentrating are all signs of low thyroid hormone levels. On the other hand, weight loss, muscle weakness, elevated blood pressure and heart rate, and a tense, irritable mood are all linked to hyperthyroidism, a condition in which thyroid levels are excessively high.

Levothyroxine: Can it raise osteoporosis risk?
The recent study’s team had previously demonstrated that levothyroxine use can result in a number of undesirable side effects, especially in those who use it excessively. In a previous study, the authors demonstrated that levothyroxine use in individuals with elevated thyroid hormone levels negatively impacted older adults’ leg mass; the findings were published in Frontiers in Aging. Both their most recent research and that study included an analysis of the Baltimore Longitudinal Study of Aging.

In their most recent study, the authors examined 32 males and 49 females who were 65 years of age or older at the beginning of the study, with a mean age of 73, in order to examine the effects of levothyroxine use on a comparable cohort of adults. To establish a quasi-control group, they matched these participants to five other cohort members based on biological sex, body mass index (BMI), age, race, history of alcohol use, history of smoking, other treatments they were undergoing, and TSH levels.

This cohort was analyzed after two visits during which Dual-Energy X-ray Absorptiometry was used to measure their bone mass and density. Over the course of the study, researchers found that people taking levothyroxine and having normal thyroid hormone levels had less bone mass and density. The findings imply that even when levothyroxine is taken at the recommended dosage, bone loss may occur in older adults, raising the possibility of osteoporosis.

Is levothyroxine overprescribed?
There have long been concerns about the overprescription of levothyroxine for elderly patients; a 2023 letter in Clinical Chemistry suggested that many people had been overdiagnosed with hypothyroidism. It referenced studies demonstrating that TSH levels fluctuate greatly throughout the year, reaching their highest in the winter and falling in the summer. By comparing the ratio of free thyroxine (T4) levels to those of people with elevated TSH levels, hypothyroidism can be diagnosed.

Hypothyroidism is the diagnosis given to people with low T4 and high TSH. Subclinical hypothyroidism is diagnosed in people with slightly elevated TSH and slightly low T4, and levothyroxine may be used as a treatment. The letter made the argument that many people were being prescribed medications that might not be helpful to them and might even cause bad, preventable side effects because normal seasonal variation in TSH levels was not taken into consideration. For patients who have unpleasant side effects, deprescribing is an option, according to Sue Clenton, MD, a consultant clinical oncologist at Sheffield, UK’s Weston Park Cancer Centre.

Levothyroxine is prescribed for symptoms such as fatigue, weight gain, cognitive slowing, and elevated TSH levels, which indicate an underactive thyroid. Deprescribing, however, might be taken into consideration if a patient’s thyroid function tests return to normal or if they experience adverse effects like anxiety, rapid heartbeat, or bone loss. The significance of careful monitoring and customized treatment plans, especially in older adults, she said, was underscored by the study.

References:
https://www.medicalnewstoday.com/articles/common-thyroid-drug-levothyroxine-linked-to-bone-mass-loss
https://mygenericpharmacy.com/index.php?therapy=68