Fibroids are the most common form of non-cancerous or benign tumours in women of reproductive age. You may hear them called other names like uterine fibroids, leiomyoma, leiomyomata, or myoma. They grow in the muscle layer of the womb (uterus). Fibroids are usually round or semi-round in shape and can range in size from a large marble to a baseball.
THE FEMALE REPRODUCTIVE SYSTEM
The female reproductive system consists of the womb (uterus), vagina, fallopian tubes and the ovaries. The ovaries are where the eggs are produced, stored, and then released into the womb for fertilising once a month during ovulation. The uterus is where a developing baby grows if an egg is fertilised and implants.
The womb (uterus) is connected to the ovaries via the fallopian tubes. The cervix is the lower part of the womb that connects to the vagina, a tube of muscle that links to the organs outside the body.
HORMONES AND THE FEMALE CYCLES
A woman’s menstrual cycle lasts approximately 28 days and includes a number of hormone interactions. These hormones are released by cells or glands and transport signals from one area of the body to another.
The “female cycle” consists of two parallel cycles:
- ovarian cycle (which affects the ovaries)
- menstrual cycle (which acts on the uterine lining of the womb).
THE STAGES OF FEMALE CYCLES
The ovarian cycle and the menstrual cycle both have three stages:
- the follicular phase
- the ovulatory phase
- the luteal phase
Ovarian cycle: a follicle (single, unfertilised egg) develops within the ovary for approximately 14 days in response to the FSH (follicle-stimulating hormone) released by the pituitary gland. As the follicle develops it releases oestrogen.
Menstrual cycle: starts with a woman’s menstruation (period). The release of oestrogen stimulates the uterine wall to slightly start to “proliferate”.
Ovarian cycle: the increase of oestrogen causes the hypothalamus to release a hormone called GnRH (gonadotrophin releasing hormone).
This GnRH then stimulates the pituitary gland to release a very large amount of LH (luteinising hormone) and FSH. A surge of LH causes the release from the ovary of a fully mature follicle (egg) that is ready to be fertilized.
Ovarian cycle: the remaining tissue where the egg developed shrinks down into a corpus luteum. This corpus luteum produces large amounts of progesterone and moderate amounts of oestrogen.
Menstrual cycle: the high levels of progesterone will cause the lining of the womb to thicken be maintained, ready to receive a fertilised egg. If the egg is not fertilised, the hypothalamus and pituitary gland will reduce or shut down the production of GnRH, LH and FSH, which will produce atrophy of the corpus luteum and a drop of progesterone secreted. This causes the lining of the womb to shed and a new cycle begins on the first day of menstruation (period).
ARE THERE DIFFERENT TYPES OF FIBROIDS?
Fibroids are described based on their location within the womb (uterus).
- Intramural fibroids grow within the muscle wall of the womb
- Pedunculated fibroids grow from either the outside or inner wall of the womb and are usually only attached to the womb by a narrow stalk
- Submucosal fibroids grow from the inner wall into the womb (uterus cavity)
- Subserosal fibroids grow from the outside wall of the womb into the pelvis
Some fibroids can exist as combinations, for example, pedunculated submucosal or pedunculated subserosal fibroids.