LOS ANGELES – The dose of testosterone required to maintain a therapeutic level in transgender men is not correlated with body mass index but does decrease with age, results from a single-center study have shown.
“At this point, there are limited data regarding the dosing of testosterone in relation to age and BMI, which is what makes our work unique,” one of the study authors,, said in an interview following the annual scientific and clinical congress of the American Association of Clinical Endocrinologists.
“Although we have guidelines regarding initiating hormonal therapy for transgender patients, such as the Endocrine Society’sfrom 2017, we do not have much data regarding the optimal dosing of testosterone in transgender men. We hope that with more research, we will have more data to drive our treatment decisions for our transgender patients.”
Dr. Echt, an endocrinology fellow at North Shore University Hospital, Manhassett, NY, and her colleague, Aren Skolnick, DO, retrospectively evaluated 40 transgender men who were treated at the medical center between July 1, 2014 and July 1, 2018. They performed univariate and multivariate mixed-model analyses to determine the relationship between testosterone dose, age, and body mass index (BMI), and Cox regression analysis to determine the relationship between time to development of each physical attribute, testosterone dose, and route of administration.
The patients ranged in age from 18 to 54 years, and their mean baseline age was 25 years. At the time of their first visit, 32 of the patients were on intramuscular testosterone, four were on subcutaneous testosterone, and five were on the transdermal form.
By the end of the study, 28 patients remained on intramuscular testosterone, six were on the subcutaneous form, five were on the transdermal form, and one had transitioned to testosterone pellets. The majority of patients (37) became therapeutic during the course of the study, and the average therapeutic testosterone level was 551.7 ng/dL.
During an average follow-up time of one year, the researchers observed no correlation between testosterone dose and BMI. However, they found a negative correlation between testosterone dose and age, with or without adjustment for BMI (P = .016 and P = .020, respectively). Adjusted for BMI, the dose decreased by 2.0 mg for every one-year increase in age.
A subgroup analysis of the new patients again revealed a negative correlation between testosterone dose and age, with or without adjustment for BMI (P = .013 and P = .019, respectively). Adjusted for BMI, the dose decreased by 2.5 mg for every one-year increase in age.
Subgroup analysis of the patients already on testosterone therapy revealed no association between testosterone dose, age, and BMI. Among the new patients, no association was observed between time to development of each physical attribute and testosterone dose or route of administration. Among the new patients, 73% reported hair growth (mean time, 89 days), deepening of voice (51 days), and cessation of menses (136 days), and 59% reported clitoromegaly (51 days).
“The finding that surprised us the most is that the testosterone dose needed to maintain a therapeutic testosterone level in transgender men is not related to BMI,” Dr. Echt said. “Some medications are dosed based on body weight, and it was surprising to us that testosterone dosing was not related to weight in kilograms or BMI. Although the findings from our project suggest that the testosterone dose needed for hormonal therapy for transgender men may decrease with older age, further research and larger studies are needed in this field to help guide management of transgender patients.”
Dr. Echt acknowledged certain limitations of the study, including its small sample size. “At this point, our population of transgender patients has been increasing in our practice,” she said. “In the future, we would like to build upon our study by including more patients in our retrospective analysis and then stratify the results by mode of administration of testosterone.”
The researchers reported having no financial disclosures.