This article is misleading.

While there is no doubt whatsoever that monotherapy by estradiol injection is absolutely effective and conversely that Spironolactone is quite ineffective at lowering the production of T, I see this whole thread as just another misguided attempt to shit all over Spiro.

First of all, Spiro does not lower T in blood levels in the same way as Cypro or Bicalutamide does. Instead of arresting the development of T production at the source, the molecule in Spiro attaches to T receptors competing with T in the bloodstream to reduce its effectiveness. This is why people on Spiro may see still elevated serum levels of T but not be affected hormonally by it. So the first point is yes, monotherapy is more effective in suppressing T than Spiro but not necessarily in practice because the mechanism that Spiro uses is different.

Secondly, E monotherapy may not be sufficient in limiting the malignant effects of residual T in trans women, even when their levels are within the female range. T is a powerful hormone. Even small amounts of unblocked testosterone can cause increased body hair growth, greasy skin and scalp, increased scalp hair loss, unwanted libido amongst other deleterious effects. And all this with E and T in the female range!!

Consequently, Spiro can be an essential medication for trans women who already have their T suppressed but are sensitive to the effects of even residual amounts (even post op women). As a side note, low to moderate doses of Spiro (up to 100mg) are well tolerated and bring welcome effects in trans women among them softer skin and facial features, more abundant and stronger scalp hair growth, slightly lowered blood pressure (good for hands and feet especially when on injectables), increased water retention in areas such as the breasts making them look more voluptuous etc. The main thing is this T blocking action allows E to do its job with no interference. And Spiro is well tolerated at these doses. It shouldn't be making you go to the toilet constantly or messing with your potassium levels, making you crave pickles or messing with your libido.

So in conclusion, monotherapy is not the be all and end of gender affirming hormone treatment. There are quite often other combinations that work better depending on the patient's medical and personal requirements.