Thyroid function and eating disorders
The thyroid is responsible for many functions within the body, but one of its most important functions is regulating metabolism - or the process that helps the body convert food into energy.
The organ produces several hormones to aid in this conversion, including T3 and T4, which help determine how much energy certain cells need and regulate body temperature and heart rate.5 But those processes can be thrown off by patterns of disordered eating.
Bulimia nervosa and other eating disorders, including anorexia nervosa (AN) and binge eating disorder (BED), have also been shown to have an impact on metabolism, usually by lowering the resting metabolic rate, or the total number of calories burned when the body is at rest.1,6,7
Thankfully, these kinds of disruptions have yet to be shown to lead to thyroid cancer, but it appears, based on previous studies, that bulimia nervosa can impact the thyroid in other ways.
Bulimia and thyroid problems
Research into the specific impact bulimia nervosa has on the thyroid has been sparse over the years, but the results have been consistent.
In two separate studies, conducted two years apart by the National Institutes of Mental Health (NIMH), researchers found that BN had an impact on patients' thyroid hormone levels - specifically the amount of T3 and T4 in someone's blood.1,2
In particular, T3 levels appeared to drop during periods when the patients were not partaking in disordered eating behaviors. This led scientists in both studies to conclude that binge-purge behavior was connected to a temporary increase in active thyroid hormone levels and metabolic rate.1
In the second study, T3 levels were found to correlate with the amount of calories, protein, fat, and carbohydrates consumed. Though scientists were unsure whether lower T3 levels during periods of abstinence were connected to lower caloric consumption during these periods, or if they could reflect hypothalamic-pituitary dysregulation.2 This second conclusion points to an impaired neurological response to acute stress, which is sometimes present in certain mental health disorders.8
Can bulimia cause thyroid issues?
In 1996, a third study was conducted to further investigate why or how bulimia nervosa impacted circulating thyroid hormones. While this study found similar results, and came to the similar conclusion that periods of binging and purging may stimulate thyroid activity, there was similar murkiness over why T3 and T4 levels dropped during periods of abstinence.3
To date, there’s a lot of conflicting opinions on the subject. Some believe the fall in thyroid hormone levels during periods of abstinence from binge-purge behaviors is an adaptation to natural changes in caloric intake. Others see it as a potential sign of thyroid dysfunction, which may call for further treatment.
It's likely future studies will be needed to clear up this issue. Though, while BN seems to affect the thyroid, at this time, thankfully, no studies have connected these issues to thyroid cancer.