@Aruna i would suggest you to grow ur hair asap. While on HRT try eating a lot of green veggies, tomatoes & a very healthy diet. your body is trying to make a lot of new changes and structures like in puberty... u shud provide ur body more than adequate nutrition during this . For good hair also consider supplementing biotin, lycopene and vitamin E . as your doctor for a healthy vitamin routine for hair.
and dont take any vitamin routine for more than a month, may be use it on alternate months, remember its only to supplement. If you are on artificial supplements for a long time , your digestive system will adapt and forget how to extract these vitamins from natural sources. so the best is to take them for a short time and alternate them.