HRT is most common in menopausal and postmenopausal women, though it has recently gained popularity in transgender women. Marla Ahlgrimm notes that Premarin was the first commercially available HRT in the United States and was formulated using urine from a pregnant mare. Premarin is an estrogen that is different from estradiol produced naturally by a women.
Marla Ahlgrimm, who began dispensing natural HRT to help her pharmacy patients manage hormonal symptoms in the 1970s, says that most doctors prescribed the same standard dose to each patient. Ahlgrimm was one of the first pharmacists to advocate the use of compounded bioidentical hormones, which are those that are identical to hormones produced naturally. Premarin utilized synthetic hormones.