59 yo. Hyst. Have ovaries. Nightly sweats and chills x 3 weeks. No temp. Menopause or something else? Seems to happen same time each night. Insomnia.

Ovaries have failed. Just as any woman of your age (59) that has not had surgery, your ovaries are succumbing to the effects of diminished estrogen production, also known as, menopause. Consult with your MD to determine if you are interested in estrogen replacement therapy or not.