Hormone therapy from the time of early menopause until age 50 is not associated with an increased overall risk of breast cancer. It is generally safe to take hormone therapy until age 50 or 51 and the described risks of hormone therapy then start from that age. Side effects are really no different. Early menopause is often of unknown cause. It may be due to chemotherapy or radiotherapy to the ovaries, may occasionally be due to genetic factors, and may be due to immune mechanisms.
Much work remains to be done on the reasons for it.
Stress is not generally regarded as a cause for premature menopause. Hormone therapy for people who have had a hysterectomy usually requires oestrogen only, unless the hysterectomy has been done because of endometriosis, in which case added progestins are also recommended. If both ovaries have been removed, then an important source of male hormones is removed and loss of libido may be a problem. If early menopause occurs naturally, the male hormone producing function of the ovary probably continues. For somebody who has had a hysterectomy, but whose ovaries are intact, the timing of menopause can be difficult to establish, but hot flushes may provide an indication.