Total and unbound cytosolic estrogen and progesterone receptors in myometrium and fibroid after gonadotropin-releasing hormone agonist treatment.

OBJECTIVE: To study the changes in bound and unbound cytosolic estrogen receptor (ER) and progesterone receptor (PR) in fibroid and myometrium after treatment with gonadotropin-releasing hormone agonists (GnRH-a). DESIGN: Prospective randomized study. SETTING: A tertiary institutional hospital. PATIENTS: Thirty premenopausal women with normal regular menstrual cycles and uterine fibroids. INTERVENTIONS: Patients were randomized to receive buserelin acetate for 3 months (n = 20) or no treatment (n = 10) before hysterectomy. MAIN OUTCOME MEASURES: Bound and unbound ER and PR. RESULTS: In nontreated women, values of unbound ER and PR in fibroid were higher than in myometrium. There were no differences in total receptors. The total and unbound ER in myometrium was higher in treated than in nontreated women. There were no differences in fibroid. CONCLUSIONS: The higher content of unbound hormone receptors in fibroid correlates with an exacerbation of the hormone dependence of this tissue compared with myometrium. The increase of total and unbound ER in myometrium after treatment suggests a higher level of synthesis or a lower level of degradation of receptors in this tissue.