To verify if the entity of the peak GH responses to the GHRH+arginine (ARG) test is able to show different degree forms of GH deficiency (GHD), we linked these responses with the number of other anterior pituitary deficits. These anterior pituitary deficits were also related with
IGF-I levels. To this purpose, we studied a large cohort of lean patients with
pituitary disease of different etiologies [86 males and 68 females; age: mean +/- SEM 41.5 +/- 1.2 yr, body mass index (BMI) <25 kg/m2]. The patients were subdivided into 4 groups according to the increasing number of
hormone deficiencies: isolated GHD (HYPO1, no.=28) or GHD plus one, two or three additional
hormones (gonadotrophin,
ACTH, and
TSH) deficiencies (HYPO2, no.=20; HYPO3, no.=15; HYPO4, no.=91). Peak GH responses to the GHRH+ARG test and
IGF-I levels showed a clear difference among the groups (p < 0.01 and p < 0.001, respectively). A significant difference was found between HYPO1 and HYPO4 for
IGF-I levels (p < 0.05), and between HYPO1 and HYPO4 and between HYPO2 and HYPO4 for the GHRH+ARG test (p < 0.005). Considering only the patients who underwent both GHRH+ARG test and
insulin tolerance test (ITT) (no.=70), the pattern of the peak GH responses to the GHRH+ARG test was the same of the whole group of patients, while no statistical difference was found with ITT. Our data show that the peak GH responses to the GHRH+ARG test and the
IGF-I levels are linked to the severity of
hypopituitarism, expressed by the number of increasing anterior pituitary deficits. This association is lost if the evaluation of the GH status is performed by the ITT. In all, the GHRH+ARG test and measurement of
IGF-I are able to evidence different degrees of GHD in adult patients with
pituitary disease.