Letro is pretty strong tbh. It commonly has reported sides, including sexual sides, and it will literally shut down all of your Estrogen. You want some estrogen, remember 'homeostasis" or normal body hormone function is the goal on HRT. This includes other hormones, not just testosterone.
I would personally recommend low dose Exemestane over the Letro. Reason being that exemestane actually shows increases in Free Testosterone levels, DHEA and FSH when used in conjunction with Test.
Common low but effective dosages would be 6.25mgs- 12.5mgs EOD. It should control your E levels just fine at those dosages, is affordable and will add benefit to your HRT cycle.
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http://www.ironmagresearch.com/products/exemestane/