Changes in the volume of residual pituitary adenomas in patients with adult-onset growth hormone deficiency during replacement therapy with the recombinant human growth hormone

In the course of a prospective study concerning recombinant human growth ho rmone replacement therapy in adult-onset growth hormone deficiency, we dete rmined the volumes of residual tumors in six patients with pituitary macroa denomas who had formerly been treated with surgery alone or surgery and ext ernal radiotherapy. Pituitary CT scans in direct coronal views were obtaine d at baseline, and at 6, 12 and 18 months. The volumes of the residual tumo rs were calculated from the tumor diameters assuming that the tumors had an ellipsoid shape. Tumor volumes did not change in one patient and were reduced in two patient s. In three patients, clinically non-significant tumor expansion by a media n of 23.6 +/- 13.2% (range, 21.1-62.0%) was noted after 12 to 18 months. Th is tumor expansion did not cause signs or symptoms of a mass effect and did not influence further treatment. One of the six patients discontinued treatment and no further change in tum or size, as determined by MRT, was noted over a mean follow up of 34 months . Treatment was continued for up to 38 months in five patients. In four of these five patients no further change in tumor size was detected. However, treatment with the growth hormone was stopped in one patient since a 30% ex pansion in tumor volume, elevating the optic chiasm, was noted on MRT. None of the patients developed deterioration of visual fields. Interestingly, t umor invasion of the cavernous sinus had been present initially in all thre e who displayed tumor expansion while on rhGH. This first study in which diameters of residual pituitary adenomas in patie nts on growth hormone replacement therapy were prospectively and carefully measured, permits no conclusion regarding a causal relationship between gro wth hormone and tumor expansion, owing to the small number of patients. How ever, the observed incidence is not much different from that in former stud ies without growth hormone replacement therapy. Nevertheless, a close obser vation of the pituitary by imaging studies at regular intervals appears to be mandatory, particularly in patients with invasive residual adenomas.