Testing pituitary function in aging individuals

GH provocative tests remain the only hormonal investigation that provides data on somatotroph function during an individual's lifespan. Diagnosis of GHD in the elderly is difficult because of age-related GH secretory decline or somatopause. In aging and adulthood, the evaluation of spontaneous GH secretion and IGF-I levels does not provide grounds for distinguishing GHD subjects from normal subjects. Thus, severe GHD must be biochemically demonstrated by provocative testing. Among classical tests, ITT is considered the gold standard, while arginine and glucagon are considered reliable alternatives. ITT, however, has contraindications that are particularly relevant to elderly subjects. GHRH in combination with arginine or synthetic GHS has become the most potent and reproducible stimulus of GH secretion because it explores the maximal secretory capacity of somatotroph cells and is independent of aging. This approach to somatotroph test function shows high specificity and very good sensitivity as it can distinguish between normal and GHD subjects even in the elderly. GHRH in combination with arginine or GHS is safe and has no known contraindications. This profile is therefore relevant in term of availability of a good provocative test for GH secretion in aging individuals. In fact, even in this period of life, diagnosis of GHD may be crucial, based on the evidence that treating GHD patients with rhGH replacement therapy counteracts several clinical symptoms that are more likely associated with GHD than aging.