The Biochemistry of Lust: How Hormones Impact Women’s Sexuality
By: Kaye Smith Phd
Tags: Health, Science, Sexuality, Sex, Women

Estrogen (Marilyn Monroe: The Venus Hormone)

Estrogen holds court on the dance floor. She is having a ball flirting and dancing. Her ample backside swings with the rhythm of the music, while her satiny skin glows. Estrogen is a total package deal with a quick wit and a strong mind. But yeah, her physical allure doesn’t hurt either. She’s impossible to ignore. Her laugh is contagious, and her hourglass curves make all her dance partners weak in the knees. She’s not afraid to make a fool of herself ether, and she falls down a few times while dancing. But that’s okay, her bones are strong and resilient. She notices Testosterone checking her out by the buffet. Wow, he is soo gorgeous and sexy, he makes her all tingly. She can feel her panties getting moist. Um…

Estrogen, the Marilyn Monroe of hormones, dominates the first half of a woman’s menstrual cycle and is opposed by progesterone in the second half. Estrogen comes in three forms: estradiol (E2), estriol (E3) and estrone (E1). Estradiol is the most biologically active hormone for premenopausal women, while estrone is more active after menopause. Estriol is primarily active during pregnancy (2).

Remember what I said about hormones being shapeshifters? One of the most fascinating facts in human physiology has got to be the fact that estradiol, the hormone most associated with femininity, is synthesized from testosterone (16).

Estrogen is responsible for more than just breasts and baby-making. It affects every part of a woman’s body and brain, and it has a profound impact on her sexual functioning. It is responsible for maintaining pelvic blood flow, the creation of vaginal lubrication, as well as the maintenance of genital tissue (17).

When estrogen is in short supply, women struggle with diminished genital and nipple sensitivity, difficulty achieving orgasm, increased sexual pain, and inadequate lubrication (17). Women with low estrogen are at risk for vaginal atrophy, which has to be among the most delightful aspects of aging (NOT).

Another issue I am intimately familiar with.

As I moved deeper into the menopausal rabbit hole, I experience vaginal irritation, dryness, and constant UTIs, all of which were due to estrogen bidding me a fond farewell. When estrogen leaves the building, the vaginal lining (the epithelium) gets thinner, the vagina itself may shrink and lose muscle tone and elasticity.

And as for those persistent UTIs that bedevil menopausal women like me, they are due to the increase in vaginal pH. When the vagina becomes more alkaline, it kills off good bacteria, leaving a woman a sitting duck for a number of vaginal and urinary tract infections.

Remember this, a happy pussy is an acidic one (ideal pH 3.8–4.2).

The normal level of estradiol in a menstruating woman’s body is around 50 to 400 picograms per milliliter (pg/mL). This fluctuates with the menstrual cycle. Below this threshold, and there is an increased risk for the problems mentioned above. When women are in menopause, estradiol levels are often as low as 10–20 (pg/mL) (17).

Estrogen: The True Lady of Lust?

Testosterone, the loud and proud androgen, is usually assumed to be the sexual mover and shaker for both men and women. Estrogen, it has been argued, just gives a woman a wet vagina, the motivation to use it comes from her testosterone.

This is the view expressed by Theresa Crenshaw in The Alchemy of Love and Lust. In contrast to men, she argues that women have four sexual drives 1. Active (aggressive) 2. Receptive (passive) 3. Proceptive (seductive) and 4. Adverse (reverse). These drives are representative of our hormonal makeup.

She differentiates along standard party lines and claims that testosterone fuels women’s active sex drive, while estrogen fuels the receptive and proceptive drives. According to Crenshaw, ever contrary progesterone doesn’t fuel anything but a nap (the adverse drive).

However, some researchers believe that estrogen’s role is underestimated in female desire and that the conversion of testosterone to free estrogen in women might play a major role in female desire. (18). “Free” in this case means a hormone that is biologically active and available for our bodies to use.

According to Emory professors, Cappelletti and Wallen, for most female mammals the most important hormone governing sexual behavior is estrogen. That would make human females rather weird and unique if our sexuality was testosterone-driven.

Plus, research does show that estrogen alone is capable of increasing desire in women(19).

Estrogen Replacement

Mode of delivery (e.g., by mouth, or transdermal) is an important and possibly overlooked factor when looking into HRT. One major problem with oral estrogen’s like Premarin (aside from the fact they’re made of horse pee!) is that when estrogen is taken by mouth it raises levels of SHBG (sex hormone-binding globulin).

SHBG is a protein secreted by the liver that binds both estrogen and androgens. It prefers androgens. This means that it will reduce free androgens and estrogens, both of which are associated with sex drive.

In a randomized, controlled study of 670 women comparing transdermal estrogen therapy with oral (Premarin), it was found that transdermal estrogen improved sexual functioning according to scores on a self-report measure. Women who used horse pee (Premarin) showed no improvement in sexual functioning and presumably had to come up with some new hobbies (20).

As a side note, I keep visualizing a poor, pregnant mare being badgered by some pharmaceutical rep going, “Just pee in the bucket Seabiscuit; we need the money!” But I digress…

Bioidentical Hormone Replacement

Women who are interested in HRT often opt for bioidentical hormones. They have become popular for a few reasons. In 2002, the WHI (Women’s Health Initiative) study dropped a bombshell on the world’s menopausal women and linked hormone replacement with a 26% increased risk of breast cancer and an increased risk of cardiovascular events and stroke. Within three months of published reports of the dire findings, prescriptions for hormone therapy (HT) dropped by 63% (21).

Also, popular books like The Sexy Years by Suzanne Somers have promoted the use of compounded bioidenticals instead of FDA approved drugs. Compounded bioidentical hormone therapy (CBHT) is custom formulated by a compounding pharmacy and tailored to the individual. They are often perceived as safer and more natural.

What Are Bioidentical Hormones?

From my readings, this may be short-sighted. First up, let’s talk about what bioidentical hormones are. According to the Endocrine Society, bioidentical hormones are “compounds that have exactly the same chemical and molecular structure as hormones that are produced in the human body.”

They are often plant-derived in comparison to the Premarin and Provera (used in the WHI study), which is a synthetic estrogen synthesized from conjugated horse urine and synthetic progestin respectively.

Note that Premarin could be considered “natural” given the fact there’s nothing more natural than horse pee! However, it isn’t identical to what your body makes.

Bioidentical progesterone is made from diosgenin that is derived from wild Mexican yam or soy, while bioidentical estrogen is often synthesized from soy. Both bioidenticals, like all hormone therapies, are extensively processed in a lab (22).

The Endocrine Society’s definition is broad and doesn’t refer to the sourcing, manufacturing, or delivery method of bioidenticals. This definition can refer to both FDA approved HRT as well as non-FDA approved hormone replacement.

There is no evidence that bioidenticals are safer than synthetic hormones. Nor, is there isn’t any evidence supporting CBHT as a better alternative. With CBHT there are issues regarding dosage, purity, and strength.

According to an article in The Mayo Clinic Proceedings, “Compounded hormone preparations are not required to undergo the rigorous safety and efficacy studies required of FDA-approved HT and can demonstrate wide variation in active and inactive ingredients.” (21).

There are several FDA approved bioidentical hormones that are on the market. They differ from CBHT in that they have some science behind them and they are carefully formulated and manufactured according to strict specifications (21).

Is Hormone Therapy Safe?

I think it depends on who you ask and what you read. It also depends on your particular situation. I recommend any woman interested in hormone replacement do some serious study on this issue. The WHI study scared the bejesus out of women, their doctors, and created a lot of hysteria. There were several issues with that study that are beyond the scope of this article.

One book I recommend is Menopause: Change, Choice, and HRT by Australian physician Dr. Barry Wren. He goes into detail about the WHI study and its shortcomings, including the fact that the women who participated in the study were older (average age 63), smokers/former smokers, overweight/obese, and in poor health.

There is a critical “window of opportunity” for women to go on HRT. It is recommended that women do it within ten years of their last period. Primarily, because going for many years without estrogen can cause permanent changes to the body that HRT could exacerbate.

For example, estrogen helps prevent cholesterol from building up in your arteries. After you have been without it for a while, your arteries will likely have some damage. Taking an estrogen, particularly in oral form, increases the presence of liver proteins that cause blood to clot.

This factor, combined with arthroscopic buildup, could lead to an increased risk of stroke or heart attack. But taking estrogen before arterial damage has occurred, and within the 10-year window of opportunity, might reduce your risk of heart attack or stroke (23).

Estrogen: Points to Remember