A hysterectomy is the surgical removal of the uterus, which carries pregnancy and generates menstrual flow. The primary function of producing and releasing eggs, known as ovulation, belongs to a separate set of organs. Therefore, continued egg production hinges on whether the ovaries remain in the body following the operation.
Defining the Surgery
A hysterectomy’s long-term biological effects depend on the extent of the surgery. The ovaries are small glands located near the uterus, and their removal is a separate procedure called an oophorectomy. Surgeons may choose to leave the ovaries intact, a process known as ovarian preservation.
A partial or subtotal hysterectomy removes only the upper part of the uterus, leaving the cervix. A total hysterectomy removes the entire uterus and the cervix. Neither procedure requires ovarian removal, though the fallopian tubes may be removed to lower the risk of ovarian cancer. If the ovaries are not removed, egg production capability remains.
The Ovaries and Egg Production
The ovaries are the dedicated structures within the female reproductive system for storing and maturing eggs. Each ovary contains thousands of follicles, which house immature egg cells. Throughout the menstrual cycle, a complex hormonal cascade involving follicle-stimulating hormone (FSH) and luteinizing hormone (LH) stimulates one follicle to mature.
The maturation process culminates in ovulation, the release of the fully developed egg from the ovarian surface. This biological event is controlled by the ovarian-pituitary axis and does not require the physical presence of the uterus. The ovaries also have the secondary function of producing sex hormones like estrogen and progesterone, which regulate the cycle.
Ovulation Without a Uterus
If the ovaries are preserved during a hysterectomy, egg production and ovulation persist, and the monthly hormonal cycle continues. A mature egg is released from the ovary around the midpoint of the cycle. However, the egg’s path after its release is fundamentally altered by the surgery.
Normally, the egg is swept up by the fimbriae, which are finger-like projections at the end of the fallopian tube, and then travels toward the uterus. Following a hysterectomy, the fallopian tubes may be disconnected or removed, preventing the egg from reaching the missing uterus. Instead, the ovulated egg is released directly into the pelvic cavity, where it is absorbed by the body.
This absorption of the egg is a natural biological process that occurs even if the egg is not fertilized. The most noticeable change after a hysterectomy with retained ovaries is the complete cessation of menstruation. Since the uterus, which holds the endometrial lining that sheds as a period, has been removed, a monthly bleed cannot occur even though ovulation is still taking place.
Hormonal Effects and Menopause
The ovaries’ continued function means they still produce estrogen and progesterone, preventing the immediate onset of menopause. Menopause is defined as the point when the ovaries cease hormone production and stop releasing eggs. The abrupt loss of ovarian hormone production, which occurs if the ovaries are removed along with the uterus, causes immediate surgical menopause.
Even when the ovaries are retained, a hysterectomy may affect the timing of natural menopause. Studies suggest women may experience menopause slightly earlier, by an average of up to four years. This earlier onset is thought to be caused by a potential compromise to the blood supply of the ovaries during the uterine removal. Retained ovaries provide the benefit of continued hormone production for several years, avoiding the sudden, severe symptoms associated with surgical menopause.