By BSc, MSc (embryologist).
Last Update: 12/18/2018

Even though Polycystic Ovary Syndrome (PCOS) was described for the first time about one century ago, the particular cause of this gynecologic and metabolic disorder is still unknown. In fact, many of the theories about the potential origin of PCOS are confusing, since sometimes the potential cause might be a consequence of the disease.

It is known that an important genetic component is involved in PCOS. However, it is not caused by a single gene, but by multiple genes along with other environmental factors such as lifestyle, nutrition, etc.

In short, it is a multifactorial disease. Due to it, the diagnosis can turn out to be a complicated process.

Insulin resistance

Insulin is a hormone that is produced and released by the pancreas. It is required for the organs to absorb the glucose present in blood. This allows the cells of each organ to have the energy they require to carry out their function properly.

Insulin resistance is a core symptom of PCOS. In fact, between 50 to 70 percent of women with PCOS, irrespective of their weight, have insulin resistance.

This means that this hormone, in spite of being correctly produced, is unable to function effectively. The organism detects that insulin levels are insufficient.

To compensate this insulin deficiency, the pancreas increase its production to massive levels, and produces an excess of it in blood. It leads to what we know as hyperinsulinemia.

As a result, insulin resistance causes, at the same time, excess insulin in blood.

Effects of high insulin levels

When insulin resistance causes hyperinsulinemia, it becomes a powerful amplifier of what we know as hyperandrogenism, since it triggers the following processes:

Increased androgen levels
Insulin promotes the synthesis of androgens in the ovary and the suprarrenal glands, favoring anovulation.
Increased LH release
An increased concentration of LH enhances the hyperandrogenic effect, since its main function is to promote the synthesis of androgens in ovarian follicles.
Decreased SHBG synthesis in the liver
Sex Hormone Binding Globulin is the main transporter of androgens in blood. The lesser its concentration, the higher the number of free androgens that can exert their function over the ovaries and other tissues.

High androgen levels

Androgens are a set of hormones, including testosterone, a hormone that is specific to adult males. Amongst its main functions we can include the development of male sex characteristics.

In women, androgens are produced in the ovaries and the suprarrenal glands, although in lesser amounts in comparison with males.

However, when androgen levels surpass the boundary line for females, the ovarian cycle is substantially compromised. Follicles fail to develop correctly and become atretic, turning into cysts and preventing ovulation, since their maturation level is insufficient for them to release eggs. This is how anovulatory cycles occur, which lowers the chances for the woman affected to get pregnant naturally.

Consequences of hyperandrogenism

In addition to causing indirect anovulation, hyperandrogenism is the main responsible of many of the most common clinical symptoms of PCOS:

Hirsutism
Abnormal hair growth in unusual areas like the face, chin, breast, back, or arms.
Acne
Presence of pimples and blackheads as a consequence of excess fat in the skin.
Biochemical hyperandrogenism
High testosterone levels in blood.

The symptoms of high androgen levels in blood require a treatment to reestablish the adequate hormonal treatment.

Obesity can cause this symptom, too. Indeed, PCOS is widely associated with metabolic disorders such as insulin resistance, which has been explained above.

For this reason, if the women has overweight in addition to PCOS, the virilizing effect of androgens can become worse, as adipose tissue increases the production of these hormones.

Acne, on the other hand, is another characteristic effect of this syndrome, which is related to an excess in the levels of male hormones. The presence of pimples and blackheads is due to increased testosterone levels, which favor the presence of fat in the skin. Excess fat in the skin clogs pores, increases the presence of bacteria, and leads to the formation of large, pus-filled pimples.

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Other potential causes of PCOS

Aside from the potential causes already described, the origin of this syndrome can be due to other causes, including:

Hypothalamic disorders

The hypothalamus is a portion of the brain that regulates body functions. One of its function is to produce one of the most important hormones in charge of regulating the menstrual cycle: gonadotropin-releasing hormone (GnRH).

GnRH is a special hormone because it is released in a pulsating way by the pituitary gland every 90 minutes.

Its effect on the pituitary land, as the name suggests, causes the release of gonadotropins FSH and LH. If the hypothalamic function fails, the releasing pattern of GnRH is altered. As a result, the same applies to the production and release of gonadotropins.

In fact, a possible explanatory theory for PCOS says that it is caused by failure in the GnRH release system.

A higher pulsatility rate in the release of GnRH causes an increased production of LH. As a result, LH levels can be three times higher than those of FSH. This leads to a greater androgen production, which prevents ovulation because LH is the hormone in charge of producing this set of hormones in the ovaries.

Liver disease

Of the varied set of functions of the liver, one of them is the synthesis of Sex Hormone Binding Globulin (SHBG).

If there is some kind of abnormality in the liver, SHBG synthesis is reduced, resulting in higher levels of free androgens in blood that can cause the common symptoms of PCOS.

As explained above, this situation can occur as a result of too high insulin levels in blood.

Disorders of folliculogenesis

Through ultrasound scan and ovarian tissue biopsies, it can be observed that PCOS patients have an increased count of growing follicles, with a growth rate that is 2 to 3 times greater than in healthy females.

This pool of follicles contains all follicles that have matured from the primordial size to a size that allows them to be seen using an ultrasound. For this reason, they are likely to be released during ovulation.

With PCOS, the number of follicles recruited monthly to start growing, among which we can find the one that will be released, is too large due to an increased concentration of estrogens, which prevents them from finishing the maturation process. This is the reason why they become atretic in the ovary, forming cysts.

FAQs from users

Do too elevated LH levels translate into PCOS?

By Victoria Moliner BSc, MSc (embryologist).

No. In the past, the results of LH levels were used as a criterion to diagnose a woman with PCOS. However, since too high LH levels are not an indicator of PCOS in all cases, this criterion was dismissed finally.

I have PCOS but my body mass index is normal, should I lose weight to improve my insulin levels?

By Victoria Moliner BSc, MSc (embryologist).

Diet and physical exercise to lose weight are general recommendations in cases of PCOS where, additionally, the woman is overweight. If you are already on your weight, you do not need to start a weight loss diet plan. In fact, losing weight can even worsen the situation.

Do all women with PCOS develop hirsutism?

By Victoria Moliner BSc, MSc (embryologist).

Although symptoms can vary from woman to woman, given the variety of symptoms associated with PCOS, hirsutism is present in almost 80 percent of the cases. In most women, androgen levels are too high, which causes this peculiar side effect.

Suggested for you

As one shall see, determining a specific cause of PCOS is a hard task. This can complicate the diagnosis at the same time. To learn more about the criteria taken into account, we recommend that you read this: Which Methods Are Used to Diagnose PCOS?

One of the main symptoms of PCOS is anovulation. Follicles are unable to develop properly, and therefore the egg cannot be releases into the Fallopian tubes. Want to learn more about this disorder? Click here: What Is Anovulation?

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.

References

Adams J, Polson DW, Franks S 1986 Prevalence of polycystic ovaries in women with anovulation and idiopathic hirsutism. British Medical Journal 293, 335–359.

Balen A, Mitcehlmore K. What is polycystic ovary syndrome? Human Reproduction 2002;
17:2219-2227.

Carmina E, Wong L, Chang L, Paulson RJ, Sauer MV, Stanczyk FZ et al, Endocrine abnormalities
in ovulatory women with polycystic ovaries on ultrasound, Hum Reprod 1997;12:905-9.

Checa Vizcaíno, M.A., Espinós Gómez, J.J., Matorras Weining, R. (2005). Síndrome del ovario poliquístico. Buenos Aires; Madrid: Médica Panamericana. Sociedad Española de Fertilidad (SEF). ISBN 84-7903-599-4.

Cheung AP, Chang RJ 1990 Polycystic ovary syndrome. Clinical Obstetrics and Gynecology 33, 655–667.

ESHRE/ASRM Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome. Fertil Steril 2004; 81:19-25.

Zawadski JK, Dunaif A. Diagnostic criteria for polycystic ovary syndrome: towards a rational approach. En: Dunaif A, Givens JR, Haseltine FP, Merriam GR (eds.). Polycystic ovary syndrome. Boston: Blackwell Scientific Publications. 1992:377-384.

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Authors and contributors

 Victoria Moliner
Victoria Moliner
BSc, MSc
Embryologist
Degree in Biochemistry and Biomedical Sciences from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Presently, she works as a Research Biologist. More information about Victoria Moliner

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