What can modify a woman's physiology

Having looked at in the last few blogs at the normal menstrual cycle in detail in terms of the major hormonal changes that occur and how it affects a women's physiology, Let's now look at some commonly experienced situations that will change a woman's physiology from that of the normal menstrual cycle.

We now know the three primary hormones which impact on a woman's overall physiology are estrogen, progesterone and testosterone. Each has its own distinct effects and, when one or the other is relatively dominant in a woman's body, it generally results in a fairly similar physiology. So regardless of the specific hormonal modifier present, two women with an estrogen-like, progesterone- like or androgen-like physiology will be considered to have a similar physiology.


While there is no truly "normal' menstrual cycle, in that the variation between two women (or within the same woman) can be extremely large, it is still possible for the cycle to become extremely disrupted. While there are less severe disruptions I will mainly focus on amenorrhea and oligomenorrhea here.

Amenorrhea refers to the absence of a menstrual cycle and is defined clinically as a lack of menstruation for 90 days or more with less than three total cycles in a year (some women will not menstruate for extended lengths of time). Strictly speaking, amenorrhea can occur under many different situations. This can include a woman who has begun to menstruate at all (called primary amenorrhea), pregnancy (where menstruation stops due to not being needed) and birth control (which deliberately shuts off the normal cycle although some bleeding may still occur). There can be numerous medical causes for amenorrhea but none of these represent the type of amenorrhea that I will discus in this blog.

Rather, I will focus only on Functional Hypothalamic Amenorrhea (FHA). As the name suggests, FHA originates in the hypothalamus, which will shut down the menstrual cycle under certain circumstances. These tend to be stress related including the stress of dieting, the stress of exercise, mental stress or some combination of the three. Physiologically, in amenorrhea, estrogen drops to about 33% of normal levels and progesterone drops to roughly 10% of normal. The normal cyclical changes are also lost and hormonal levels of both are effectively a flat line. The release of LH and FSH, which I described briefly in the last blog, also disappears such that the follicle never matures or implants, the corpus luteum doesn't develop and there is no uterine lining to shed (hence the lack of bleeding). When amenorrhea develops, a woman's physiology changes enormously.


Oligomenorrhea refers to an infrequent or delayed menstrual cycle and is defined clinically as a cycle that only occurs every 35-90 days (recall that the normal menstrual cycle occurs within 24-32 days). In contrast to amenorrhea where a woman's primary hormones drop to low levels and show no cyclical changes, in oligomenorrhea those hormones are lowered but are still changing. On some days hormone levels may be identical to the normal menstrual cycle but on others their levels will be random. Like amenorrhea, oligomenorrhea can occur for many reasons.

This includes some types of birth control (where light bleeding may occur) and a variety of medical conditions (including PCOS, discussed below).

There are two types of oligomenorrhea. The first is part of the continuum of adaptations to dieting that can lead to amenorrhea. While all women were originally thought to have this type of oligomenorrhea although it's now known that there is a subgroup of women who are oligomenorrheic due to elevated androgen/testosterone levels.


In the last blog, I mentioned that the term androgen is sort of a catch-all for a variety of hormones that are produced in the body including testosterone, DHEA, DHEA-sulfate and a few others but I'll continue to use the term androgen or testosterone generally throughout these blogs. When those levels are elevated above normal, this is referred to as hyperandrogenism. Here I am combining two slightly different hormonal situations which are absolute and relative hyperandrogenism. Absolute hyperandrogenism will refer to any situation where a woman's testosterone levels are elevated above normal. Relative hyperandrogenism will refer to a situation where testosterone levels are not elevated above normal but estrogen and progesterone levels have decreased so that androgens are relatively higher.

Here we are only going to look at absolute hyperandrogenism, when a woman's testosterone levels are elevated above their normally low level along with the implications that has. Given the effects of testosterone, overall the effect of absolutely hyperandrogenism is some degree of masculinization or virilization of a woman's body with an increased prevalence of male secondary sexual characteristics along with other potentially negative effects. This includes increased body and facial hair, oily skin, acne and an increased risk of hair loss. Hyperandrogenic women often have a more "male" like body in that they have narrower hips and tend to carry relatively more of their body fat around their midsection. Relevant to this blog, women with elevated testosterone levels often show an increased amount of muscle mass along with potentially improved sports performance and an ability to respond to training.

Probably the most common cause of elevated testosterone in women, and the one I suspect most readers are at least passingly familiar with, is Poly-Cystic Ovary Syndrome or PCOS. PCOS has been found in somewhere between 6-20% of women and one of the most common effects is either oligomenorrhea, amenorrhea or infertility (due to a lack of an egg being released). In fact, roughly 15-20% of women who are infertile are diagnosed as having PCOS. PCOS is often associated with weight gain and obesity with more fat being carried around the midsection. Here even small amounts of weight loss (5-10% of current body weight) drastically improve health markers and fertility. Interestingly, while PCOS women often report having trouble losing weight, research shows no difference in weight loss between PCOS and non-PCOS women, at least within tightly controlled research.

PCOS is clinically diagnosed according to the Rotterdam criteria and requires that two of the following three symptoms be present: multiple cysts on the ovaries, clinical or biochemical signs of hyperandrogenism, and either oligomenorrhea or anovulation (an egg is not released). Practically this means that there are four distinct types of PCOS. A woman could have all three symptoms or any combination of two symptoms (i.e. cysts+hyperandrogenism, cysts+oligomenorrhea/anovulation, or hyperandrogenism+oligomenorrhea/anovulation). When hyperandrogenism is present (and this will usually manifest with oily skin, acne, central fat distribution or hair loss), the PCOS woman's testosterone levels may be 2.5-3 times a woman's nor