A California-based endocrinologist warns a recent study that found limited risk associated with high doses of testosterone given to females identifying as male is actually hiding greater dangers.

Michael K. Laidlaw, M.D. and colleagues wrote a letter to the editor of the Journal of Clinical Endocrinology & Metabolism (JCEM) regarding a study by Milou C. Madsen, et al, published in the journal in February.

The study, which attempted to measure the risk of erythrocytosis, an increase in the number of red blood cells due to the administration of testosterone to females seeking to transition to male, uses a methodology that leads to “a significant undercount of patients who may ultimately be at risk for cardiovascular events,” Laidlaw et al assert in their letter.

“In our opinion, the study by Madsen et al. in JCEM hides the true numbers of trans males at risk for high red blood cell counts and therefore cardiovascular harms,” the authors write at website Gender Sanity.

They explain differing red blood cells lab measures for the two sexes:

Males and females have different laboratory ranges for hematocrit (red blood cells).

For adult men the range is 38.3 to 48.6 percent.

For adult women the range is 35.5 to 44.9 percent.

High testosterone levels can directly cause high levels of hematocrit.

Females who identify as trans males are given very high doses of testosterone to attempt to bring their testosterone levels into the male range.

“Women who identify as trans males are being given very high, very risky doses of testosterone,” Laidlaw explained to Breitbart News about his concerns. “These high doses lead to high red blood cell counts. High red blood cell counts can lead to heart attacks and death. We believe these risks are being hidden.”

“Males and females have different normal ranges for red blood cell counts,” he elaborated. “We believe that the authors’ use of the male range for females hides a large number of females who will be at risk for heart disease and death.”

Laidlaw and colleagues, Andre Van Mol, M.D., Quentin Van Meter, M.D., and Jeffrey E Hansen, Ph.D., note results of the 1994 landmark Framingham study which showed “having high red blood cell counts (erythrocytosis) puts females at increased risk of cardiovascular disease, coronary heart disease and death due to both.”

“Studies of trans males have already shown up to a nearly five fold increased risk of myocardial infarction compared to females not taking testosterone,” the doctors explain at Gender Sanity, adding:

In the study we have critiqued, the authors use what is considered very high hemoglobin levels in males (greater than 50) for trans males (females). This is a difference of 5 whole units compared to the Framingham study (greater than 45). This difference leads to a dramatic undercount of the number of females who will likely be at increased risk of cardiovascular disease and death because of high red blood cell counts due to very high levels of testosterone.

“Physicians advocating for high levels of testosterone, such as Stephen Rosenthal, have argued that a person’s gender identity should determine these hormone levels,” Laidlaw et al observed.

The endocrinologist explained to Breitbart News transgender industry physicians “believe a person’s gender identity (which is a mental belief) can change physical reality and, therefore, what constitutes normal laboratory ranges for males and females.”

“This is, of course, impossible,” Laidlaw said. “Not only that, it’s also dangerous because doctors will miss a large number of trans males who are risking heart attacks and death from testosterone.”

Laidlaw and his colleagues instead “propose that the female reference range for hemoglobin and hematocrit be used for trans males so that both clinicians and patients can help more accurately assess risk factors for cardiovascular disease and death.”

Additionally, Laidlaw issues a warning about adolescent girls being considered for testosterone treatments.

“Because adolescents are prone to risk-taking and lack maturity, we believe that they should never be prescribed testosterone,” he said.