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Alpha- and LHbeta-subunits in vivo and in vitro in patients with nonfunctioning pituitary adenomas

Paradoxical responses of gonadotropins and their subunits to TRH have been reported in patients with clinically nonfunctioning pituitary adenomas (NFPA). In the present study we have made an in-house RIA for measuring of LHbeta-subunit. Reagents were donated by NIH, Bethesda, USA. We have measured LHbeta and alpha-subunit (alpha-SU) responses to TRH in 33 patients with NFPA and their concentrations in cell culture media in 9 NFPA. The control group were 6 patients without evidence of pituitary adenoma. Thirteen of 33 patients (39.4 posto) had significant serum LHbeta responses to TRH and 18/33 (54.5 posto) had significant alpha-SU responses. Six of nine (66.7 posto) cultivated NFPA secreted LHbeta and 8/9 (88.8 posto) secreted alpha-SU into the cell culture media. A significant correlation was obtained between the quantity of alpha-SU secreted in vitro and the maximal percent response to TRH in vivo. The results indicate that the majority of NFPA (75.8 posto) can be recognized as of gonadotroph origin by a combination of LHbeta and/or alpha-SU response to TRH. All patients who had responded to TRH in vivo secreted gonadotropin subunits in vitro.

TRH test; nonfunctioning pituitary adenomas; alpha and LH beta subunits

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