Testosterone Patch's Effects on the Cardiovascular System and Libido

The purpose of this study is to examine the effect of the testosterone patch, in addition to hormone replacement therapy (HRT), on blood vessel walls, insulin levels and sexual desire.

A woman's ovaries produce the hormone testosterone during her reproductive life but testosterone levels decline with age or when the ovaries are removed. Testosterone has been associated with sexual desire in both men and women. Low testosterone is also believed to cause symptoms of low energy. Thus testosterone is increasingly used in hormone replacement regimens to restore libido and energy in postmenopausal women.

In the past testosterone has been administered orally or via subcutaneous implants. Recently testosterone patches have been licensed for treating low libido in postmenopausal women. The testosterone patches deliver a dose of testosterone equivalent to the levels produced by the ovary during a woman's early reproductive years.

Oral testosterone can lead to changes to insulin and cholesterol levels which increase the risk of heart disease. On the contrary, testosterone patches may reduce or avoid this risk. To date, trials have predominantly focused on safety data in terms of side effects and basic blood tests. Reviews of the safety of testosterone replacement have emphasised the need for improved safety data, especially in terms of cardiovascular risk.

The investigators hypothesis that transdermal testosterone, in addition to HRT, will have no adverse effects on blood vessel walls and insulin levels and that transdermal testosterone significantly improves sexuality and psychological well-being in postmenopausal women.

Trial design:

The investigators aim to recruit 20 postmenopausal women to wear the testosterone patch for 3 months in addition to their usual hormone replacement therapy.

There will be 3 study visits - a pre study visit, week 6 and week 12. At each visit the following procedures will be performed:

* Medical history and physical examination
* Blood sample - for hormone levels, lipids and insulin levels
* Blood vessel stiffness measurements This will be performed using a small ultrasound device at the wrist with blood pressure measured every 5 minutes.
* Endothelial function (function of your arterial wall) is measured using a blood pressure cuff on each arm and finger probes on one finger of each hand. The blood pressure cuff is inflated for 5 minutes and is then deflated quickly. The finger probes will record the readings throughout this study.
* Sexual satisfaction questionnaire

Eligibility Criteria:
Inclusion Criteria:

* healthy postmenopausal women
* 45 to 70 years of age
* on HRT and willing to continue the same HRT regimen for the next 6 months
* are in a stable relationship which was started at least 6 months ago
* continue on any concomitant medications without any change during the study
* give informed consent.

Exclusion Criteria:

* have dyspareunia
* have received testosterone implants within the last 12 months or other androgen therapy within the last 6 months
* have received any medications which may interfere with the study (SSRI, anti-androgens, PDE5 inhibitors, DHEA, SERMS)
* have a significant psychiatric disorder
* have a history of breast cancer
* have diabetes, thromboembolic disorders, cardiovascular disease, any condition affecting carbohydrate metabolism, uncontrolled hypertension and uncontrolled hyperlipidaemia
* are on tibolone (due to its androgenic effect).