Testosterone in Women
Androgens are traditionally viewed as ‘male' hormones, but they are very important for women...so in fact androgens are male and female hormones.
What are androgens?
Androgens are hormones produced by both the ovaries and the adrenal glands in women, and by the adrenal glands and testes in men. They are known mostly for their masculinising effects in men, namely, beard growth, deeper voice, balding, muscle strength and potency. The main androgen in women is testosterone.
The adrenal glands produce hormones we call loosely call androgens but are really "pre-androgens" as they are the main source of both testosterone and oestrogen production after menopause. The level of one of the adrenal pre-androgens known as DHEA-S in the blood stream is higher than any other human steroid except cholesterol.
- In women before menopause, 50% of testosterone is produced by the ovaries and released directly into the blood stream. The other 50% of testosterone in the blood stream is made from conversion of the adrenal pre-androgens ( DHEA and androstenedione) to testosterone in other parts of the body
Women need testosterone in order to make oestrogen in their bodies
- The ovaries make oestrogen by converting testosterone or DHEA to oestrogen.
After menopause the ovaries stop making oestrogen. As a result the main site of oestrogen production in postmenopausal women is fat tissue. Oestrogen is also made in bone, the brain and the lining of blood vessels. The oestrogen that is made in these places in postmenopausal women is made from the hormones released from the adrenal glands, notably, DHEA.
Very little testosterone circulates freely in the blood stream. Instead 98% of testosterone is bound tightly to a protein known as sex hormone binding globulin (SHBG). This is important when considering testosterone excess and testosterone deficiency.
- Factors which lower SHBG will result in more free testosterone circulating and therefore affected women are more likely to experience hairiness or acne
- In contrast, factors which increase SHBG will result in more testosterone being bound up and less being free
- Oestrogen therapy, either as the oral contraceptive pill or tablet forms of hormone replacement therapy increases SHBG, resulting in reduced free testosterone and may cause lessened sexual desire and libido as a side effect
Testosterone levels vary during the menstrual cycle just like other ovarian hormones, with testosterone peaking during the middle of the menstrual cycle, around the time of ovulation. Some believe this may be an in built stimulus to increased sexual activity in women close to ovulation and therefore nature's way of enhancing sexual activity close to ovulation and therefore increasing the likelihood of a pregnancy.
Changes in androgens with ageing
Ageing affects female androgen production by two different mechanisms:
- With increasing age the adrenal glands produce progressively less androgens, specifically less DHEA, which are important sources of oestrogen and testosterone in elderly men and women. Why this happens is not known nor are the specific effects of the decline in DHEA well understood
- TESTOSTERONE levels in fall with age, starting from when women are in their mid to late 20's.
By the time women are in their late 40's their testosterone level has fallen to about half of what it was in their 20's. There is no further change in testosterone as women go through natural menopause, but levels do slowly decline with increasing age.
Women who have their OVARIES SURGICALLY REMOVED experience a sudden drop in blood testosterone levels.
Other circumstances which cause lower androgen levels in women include:
- Adrenal failure ( this can be surgical or due to autoimmune disease)
- Suppression of adrenal function by corticosteroid medication (such as prednisolone)
- Ovarian failure due to chemotherapy, radiotherapy, drug induced or other causes of premature ovarian insufficiency
- Pituitary failure. In this case the pituitary may not be triggering the ovaries and / adrenal glands to function normally
- Anti-androgen therapy: this may be used to treat acne or excessive body/ facial hair in women
- The oral contraceptive pill- this ‘switches off' the ovaries so testosterone production drops
The above advice is a general guide and was accurate at the time of production of this document. [August 2013]. This information is provided to complement, not replace, the advice of your health professional.