Sex hormones and the female urinary tract.
Symptomatic clinical changes and urodynamic changes are apparent in the female urinary tract system during pregnancy, the menstrual cycle and following the menopause. The sex hormones exert physiological effects on the female urinary tract, from the ureters to the urethra, with oestrogens having an additional influence on the structures of the pelvic floor. High affinity oestrogen receptors have been identified in bladder, trigone, urethra and pubococcygeus muscle of women. Oestrogen pretreatment enhances the contractile response of animal detrusor muscle to alpha-adrenoceptor agonists, cholinomimetics and prostaglandins, as well as enhancing the contractile response to alpha-agonists in ureter and urethra. Progesterone on the other hand decreases tone in the ureter, bladder and urethra by enhancing beta-adrenergic responses. The dependence on oestrogens of the tissues of the lower urinary tract contributes to increased urinary problems in postmenopausal women. Urinary symptoms due to atrophic mucosal changes respond well to oestrogen replacement therapy. However, because they recur when treatment is stopped, continuous therapy with low dose natural oestrogens is recommended. Oestrogens may be of benefit in postmenopausal women with stress incontinence, but the doses necessary for clinical effect are higher than for the treatment of atrophic urethritis. The practice of adding a progestagen to long term oestrogen therapy to reduce the risk of endometrial carcinoma may, however, exacerbate stress incontinence by decreasing urethral pressure. Cyclical therapy with oestrogens may therefore be more appropriate particularly in women who are not suitable for surgery or have a mild degree of stress incontinence, along with other conservative measures such as pelvic floor exercises and alpha-adrenoceptor agonists. The place of oestrogen therapy in motor urge incontinence has not been determined. The risk of developing endometrial carcinoma as a result of long term high dose oestrogen replacement therapy must be borne in mind but remains to be clarified. However, oestriol has less of a uterotrophic effect compared to other oestrogens in standard therapeutic doses and is to be preferred. Side effects are usually dose related and tend not to be a problem with low dose therapy.