New technique for quantitation of pituitary adenoma size: use in evaluating treatment of gonadotroph adenomas with a gonadotropin-releasing hormone antagonist.

Abstract

Because administration for 1 week of the GnRH antagonist Nal-Glu GnRH had been shown to decrease FSH secretion from supranormal to normal in men with gonadotroph adenomas, we investigated the effect of prolonged administration of Nal-Glu on the size of gonadotroph adenomas. To quantitate the effect of Nal-Glu GnRH on gonadotroph adenoma size, we first developed a technique for calculating adenoma volume. The technique involved collecting magnetic resonance (MR) imaging data from each adenoma at 1-mm slice intervals in the coronal, axial, and sagittal views and using the Softvu computer program to calculate adenoma volume from the MR data. The precision of this technique, as judged by the coefficients of variation of the calculations of the same view of the same study three times, was 1.7%, 1.0%, and 1.0% for each of three studies. When Nal-Glu GnRH (5 mg, sc, every 12 h) was self-administered for 3-12 months to five men with gonadotroph adenomas and supra-normal serum FSH concentrations, the serum FSH concentrations decreased to normal or below normal for the entire treatment period. Adenoma size, however, did not change during treatment in any of the five men. We conclude that calculating pituitary adenoma volume from MR data using the Softvu computer program is a highly reproducible technique, but that Nal-Glu GnRH is not an effective treatment for reducing gonadotroph adenoma size. The failure of Nal-Glu to reduce adenoma size despite its success in reducing FSH secretion suggests that FSH secretion from gonadotroph adenomas is dependent on endogenous GnRH, but growth of gonadotroph adenomas is not.

A Spontaneous and Severe Hyperstimulation of the Ovaries Revealing a Gonadotroph Adenoma1

“…Furthermore, the efficacy of GnRH agonist treatment has not been proven (19). Interestingly, no reduction in size has been reported after antagonist treatment of gonadotroph adenomas (20,21). The bromocriptine therapy was remarkably efficient in reducing PRL levels, but the volume of the adenoma was not modified, consistent with failure of tumor shrinkage with dopamine agonist therapy previously shown in 76 of 84 well characterized gonadotroph adenomas (22).…”

Pituitary tumors: pathophysiology, clinical manifestations and management.

“…The GnRH antagonist (Nal-Glu) was effective in normalizing FSH levels, but not in reducing tumor size when tried over a 3-12 month period. The discordant effects of the drug on tumor growth and serum hormone concentrations were postulated to be caused by the presence of factors other than GnRH controlling tumor growth (McGrath et al 1993).…”

Reduction of Plasma Gonadotropin Levels and Pituitary Tumor Size by Treatment with Bromocriptine in a Patient with Gonadotropinoma.

“…McGrath et al (38) reported that in five men with FSH-secreting pituitary adenomas, the GnRHantagonist Nal-Glu GnRHadministered for 3-12 months decreased serum FSHconcentrations to normal or below normal. Adenomasize, however, did not change during the treatment in any of the five patients.…”