Clinical applications of GnRH analogs

The effect of gonadotropin-releasing hormone agonist on thyroid-stimulating hormone and prolactin secretion in adult premenopausal women

OBJECTIVE

To investigate the effects of chronic administration of GnRH agonists (GnRH-a) on pituitary TSH and PRL secretion in adult women.

DESIGN

Prospective case-controlled study.

SETTING

Academic division of Reproductive Endocrinology, Department of Obstetrics and Gynecology.

PATIENTS

Ten ovulatory women and 10 women treated with monthly depot injections of leuprolide acetate (3.75 mg) were studied.

INTERVENTIONS

All subjects underwent pituitary stimulation with human thyrotropin-releasing hormone (TRH), 500 micrograms IV.

MAIN OUTCOME MEASURES

Basal and post-TRH-stimulated serum levels of TSH and PRL at 15, 30, 45, 60, 90, 120, and 180 minutes were compared among the two groups. Also, basal of T4, triiodothyronine, and triiodothyronine resin uptake studies were obtained and compared among the GnRH-a-treated and control groups.

RESULTS

No statistically significant difference between baseline or TRH-stimulated serum TSH and PRL could be detected between control and GnRH-a-treated groups of women. Furthermore, these groups were similar with respect to routine thyroid function assays.

CONCLUSION

Gonadotropin-releasing hormone agonist does not significantly affect baseline or TRH-stimulated TSH and PRL levels nor basal serum T4 and triiodothyronine levels or triiodothyronine resin uptake in adult women.

Stability of gonadorelin and triptorelin in aqueous solution

The influence of pH, temperature, various buffer species at different concentrations, and ionic strength on the stability of gonadorelin and triptorelin in aqueous solution has been studied using stability-indicating high-performance liquid chromatographic methods. The degradation behavior of both peptides is similar. The maximum stability of both peptides was shown to be at an approximate pH of 5.0. Acetate has the most favorable effect on stability, while phosphate causes higher degradation. Varying the concentration of acetate buffer does not affect the degradation behavior of the peptides. A higher phosphate concentration in buffer solutions causes higher degradation, however. The ionic strength of buffer solutions has no significant influence on stability. Solutions of gonadorelin and triptorelin, respectively, buffered with acetate (0.1 M, pH 5.0) with 3% (w/v) mannitol as an additive show a predicted t90% of 9.0 years and 7.7 years at 20 degrees C, respectively.

The effect of gonadotropin-releasing hormone agonists on growth hormone secretion in adult premenopausal women

Suppression of the pituitary-gonadal axis by the administration of gonadotropin-releasing hormone agonists (GnRH-a) has been used for a variety of endocrinological and gynecological disorders. The suppressive effect of GnRH-a on luteinizing hormone, follicle-stimulating hormone, and sex steroid production is well documented. However, little is known regarding the effect of GnRH-a on other aspects of pituitary function. The purpose of the present study was to determine the effect of GnRH-a treatment on growth hormone-releasing hormone (GH-RH)-stimulated GH release in premenopausal women. Eight control women and seven women, who were receiving a GnRH-a, were recruited. Before and after a bolus infusion of human GH-RH, blood samples were obtained over 3 hours and analyzed for GH by immunoassay. Basal GH and insulin-like growth factor levels were not statistically different between the two groups. However, basal levels of estradiol and the integrated GH response after GH-RH were significantly lower in the GnRH-a treated women. The reduction in GH-RH-stimulated GH release in GnRH-a treated women may be attributed to diminished endogenous estrogen secretion, or to direct pituitary suppression by GnRH-a, or both.