i used to keep two hands full of talons, back before HRT. Women used to make comments along the lines of, "You have such pretty nails, I hate you." Female customers would even sometimes grab my hands to look at them.
I was on biotin for several years, and my nails never chipped or broke or cracked except when I didn't take it. It got to the point where I cut back my dose because my nails had become so strong, that they could no longer flex... and long, inflexible nails, lead to bad injuries when you work with heavy things sometimes.
HRT has annihilated them. I keep them short now and they chip all the time. I've been told by an older coworker who has ridiculous talons, while doing lots of hand work, that you have to use nail oil to keep them moisturized. Makes sense.
I personally am lazy, so even though I can paint my nails whenever I want, I never do it. However, the idea that I don't have to worry about harming my precious, immaculate nails, is somewhat comforting - if you have super short nails to begin with, who cares if you paint them frequently? *shrug*
From reports here, your nails go to crap on MTF HRT. I dont think it's a medical concern.
For what it's worth, I was on at least 5mg of biotin/day. I went up to 10mg for a while before they got too strong. If you are pre-hrt, a month on 5mg/day will change your nails completely.