Diagnosis of PCOS

Hormonal investigations

Blood tests can be used to measure the levels of FSH, LH and circulating male hormones. The circulating male hormones that can be measured include testosterone, but more importantly is the amount of free testosterone, which is not bound to the protein that carries it around in the bloodstream.
A male hormone precursor is often raised in PCOS. This is called dihydroepiandrosterone sulphate (DHEAS) and is one of the most commonly elevated male hormones in PCOS. Symptoms of male hormone excess are more important than measuring blood levels of male hormone.

A significant number of patients with PCOS will have a reversal of the ratio of the FSH and LH levels present in their blood. Normally FSH levels are somewhat higher than LH. In patients with PCOS the LH levels are often higher than the FSH levels.

Ultrasound scans (USS)

Patients with PCOS have characteristic findings when a scan (often transvaginal) is performed of their ovaries. The little developing follicles usually sit under the surface of the ovary but do not invade the centre of the ovary. These follicles (which can look like block holes on ultrasound) are usually about 6 to 10 mm in diameter and form a ring around the surface of the ovary. A solid white centre can be seen to the ovary. This sign is called the pearl string sign because it looks like a string of black pearls around a white neck. Polycystic ovaries may also seem increased in size on ultrasound scan.


Many patients with PCOS, particularly those who are having trouble becoming pregnant will have a laparoscopy. A laparoscopy is an operation whereby the patient is given a short general anaesthetic, a small cut is made in the umbilicus, and a telescope is inserted to look at the pelvic contents including the uterus, tubes and ovaries.

At laparoscopy PCOS ovaries look rather like ping-pong balls. The white capsule of the ovary is thickened and the ovary is often very rounded. At the laparoscopy, checks will also be made to assess the health of the fallopian tubes and to look for any associated endometriosis.


Hysteroscopy is an operation whereby a fine telescope is used to look inside the cavity of the womb (uterus). This is particularly important where the patient has had significant abnormal bleeding. Abnormal areas in the uterus can be seen and specific biopsies taken to assess for cancerous or pre-cancerous changes.