Disclaimer: I am not a medical professional and this is not medical advice.
While spironolactone is widely used as a part of transfeminine hormone therapy (particularly in areas such as the United States where the antiandrogen cyproterone acetate is not available) to inhibit the masculinizing action of testosterone in those who still have testes, this is not the purpose it was originally meant to serve. Instead, it’s one of a class of drugs known as potassium-sparing diuretics used to treat high blood pressure and congestive heart failure by promoting greater excretion of water through urination, reducing blood volume and therefore reducing blood pressure; in this role, its antiandrogenic action is a side effect.
Because it is a diuretic, spironolactone is commonly accompanied by the irritating side effect of more frequent urination. And because it does not result in the loss of potassium through excretion in urine, it has the potential to produce dangerously high levels of potassium, known as hyperkalemia. However, the actual extent of that risk has been a source of confusion in trans communities for many years. One widely reblogged Tumblr post shared an image of trans adult performer Bailey Jay posing with a banana, accompanied by one user’s commentary asserting that consuming a banana could actually put trans women in life-threatening danger due to the effects of spironolactone. (I’m fairly certain that the focus on bananas as a rich source of potassium comes from a generation’s familiarity with the third entry in the ”Honey, I Shrunk the Kids” series, in which the potassium content of bananas is prominently highlighted.)
But how much of a risk do potassium-rich foods actually pose to those taking spironolactone? In populations not suffering from heart failure, it would appear there is not much of a risk at all – certainly not to the point of a healthy person needing to change their typical diet. Because of its antiandrogenic effect, spironolactone is also used as a treatment for acne in cisgender women. Plovanovich, Weng, & Mostaghimi (2015) examined the medical records of 974 cis women who were taking spironolactone for acne and the rate of occurrence of hyperkalemia among this group, comparing this to baseline rates of hyperkalemia among this population when not taking spironolactone. 0.72% of patients taking spironolactone experienced hyperkalemia, compared to a baseline rate of 0.76%. In this dataset, spanning 2000 to 2014, no actual adverse events resulting from elevated potassium levels were observed, “indicating that any mild hyperkalemia was clinically insignificant.” Moreover, after followup testing of those patients who did have elevated potassium levels, these values were now found to be normal, “suggesting that the original measurements were erroneous or that the mild hyperkalemia was transient and quickly self-resolved.” Among this population, the authors could not “identify any instances of persistent and clinically meaningful hyperkalemia in 14 years of clinical data”.
Layton et al. (2017), reviewing Plovanovich et al. and other studies, concluded that “routine potassium monitoring is largely unnecessary unless risk factors are present.” However, Thiede et al. (2019) did recommend potassium monitoring in cis women over the age of 45 taking spironolactone for acne, on the basis that hyperkalemia was observed in 1 of 112 women aged 18-45 and 2 of 12 women over 45. In terms of the transfeminine population specifically, Millington, Liu, & Chan (2019) reported that of 88 trans youth with a mean age of 16.6 years treated with spironolactone at Boston Children’s Hospital, only 2.2% of these youth experienced hyperkalemia, and all of these measurements returned to normal when potassium levels were taken again. Additionally, none of them experienced actual symptoms of hyperkalemia, and the researchers stated that “Routine electrolyte monitoring in this population in the absence of other medical comorbidities may be unnecessary.” Nevertheless, the Endocrine Society’s clinical guidelines for endocrine treatment of trans people (Hembree et al., 2017) recommend that “For individuals on spironolactone, serum electrolytes, particularly potassium, should be monitored every 3 mo in the first year and annually thereafter”. And the comprehensive metabolic panel (CMP), a typical component of regular blood tests for trans people on HRT, includes the measurement of potassium levels. Trans women and transfeminine people taking spironolactone are unlikely to experience hyperkalemia; when they do, they typically do not experience symptoms of hyperkalemia or adverse events; and routine blood tests this population already undergoes would detect hyperkalemia.
It’s also worth considering that a wide variety of foods that are commonplace in many diets contain an amount of potassium comparable to or greater than that of bananas. A trans woman eating a banana is taken as cause for concern – but nobody seems to bat an eye when we enjoy potatoes, spinach, avocados, sweet potatoes, butternut squash, black beans, tomato paste, or coconut water. Somehow, french fries just haven’t achieved the same notoriety in relation to trans women as bananas, but if bananas were truly worrisome, trans women on spironolactone would regularly be experiencing the effects of elevated potassium simply from eating many of the foods that most people consume regularly. Those trans people who express worry about the impact of eating a banana might well be ingesting copious quantities of potassium already without realizing it or noticing anything is amiss – because, most likely, nothing is. ■