Introduction

In the last decade there has been increasing interest in administrating low doses of testosterone to pre and postmenopausal women, particularly to help with loss of libido. The use of testosterone to manage low libido in women has extensively been reviewed in the medical literature for decades.

There is universal acceptance amongst reproductive endocrinologists, gynecologists and those specializing in the area of women’s health that female sexual dysfunction affects a substantial proportion of women. This has significant psychological ramifications and can adversely affect social and personal relationships. Various studies indicate that between 30-43% of women aged between 18 and 59 years of age experience some degree of sexual dysfunction.

Classifications and defining criteria for sexual dysfunction in women have been established over the past few years. Validated assessment scales and questionnaires have been developed to assist with the diagnosis and monitoring of management regimes for sexual dysfunction (see Physician Assessment Tools).

Female sexual dysfunction is a multifactorial condition that requires careful evaluation and may involve several management strategies. The hormonal profile of the subject is part of the assessment to determine the origins of sexual dysfunction.

It is considered that the hormone testosterone exerts greatest influence on human sexual function.

Testosterone is a vital component of female sexuality, enhancing interest in initiating sexual activity and response to sexual stimulation. It is also the hormone associated with greater well-being, with increased energy and vitality and with reduced anxiety and depression.

Surgically menopausal women and women with premature ovarian failure are among the populations most likely to experience a testosterone deficiency, a syndrome characterized by blunted or diminished motivation; persistent fatigue and lethargy; decreased sense of personal well-being; low circulating free testosterone or free androgen index (FAI) < 2; adequate plasma estrogen levels; and low libido.

In contrast to estrogens serum androgen levels do not fall precipitously at the time of menopause, but rather decline with age particularly after the age of 40. Total testosterone levels in women in their forties are approximately 50% of those of women in their twenties.

The main androgens in serum are testosterone, dehydroepiandrosterone (DHEA) and androstenedione (AD).

Androgenic precursors are principally made by the adrenal glands and the ovaries and in serum the principal androgen is testosterone. Sex hormone binding globulin (SHBG) is a hepatic-derived protein, which binds testosterone and oestradiol (E2), however SHBG binds testosterone more avidly than oestradiol. Thus under normal circumstances SHBG is saturated with testosterone and free (biologically active) testosterone amounts to only a few percent of total testosterone. SHBG production is inhibited by androgens and increased by oestrogens (particularly given orally).