For many years, growth hormone deficiency (GHD) was not thought to be associated with adverse effects in adults. We have since learned that GHD may lead to impaired quality of life, cardiovascular disease, impaired exercise capacity, decreased muscle mass, and increased low-density lipoprotein (LDL) cholesterol. Diagnosing and treating GHD have become important. Recognized etiologies of GHD include hypothalamic and pituitary dysfunction, such as macroadenomas (secreting and nonsecreting), apoplexy, Sheehan's syndrome, and craniopharyngiomas. Less established is how nonsecreting, nonfunctioning microadenomas (“incidentalomas”) affect growth hormone secretion. Incidentalomas are considered by many as benign lesions; however, there is suspicion that they may exert adverse consequences on pituitary function, including GHD. In this study, we evaluated 20 patients with an IGF-1 less than one standard deviation (SD) below the mean for age and sex and symptoms of GHD (including fatigue). Dynamic MRIs were obtained and patients with microadenomas and no evidence of a secreting tumor were further evaluated with the arginine-GHRH stimulation test. Nine out of 20 had an abnormal provocative test (peak GH < 9 ng/mL) and 11/20 had a normal test. In the patients who failed the stimulation test, the mean peak GH was 6.21 ± 0.64 ng/mL. The mean peak GH in the 11 patients with normal results was 29.9 ± 6.26 ng/mL. Studies have shown that obesity can lead to GHD and GHD can cause obesity. This initiated us to analyze our patient's BMI. The mean BMI of the patients who failed the arginine-GHRH stimulation test was 32.31 ± 8.68 and the mean BMI of the patients with a normal test was 26.85 ± 4.50. The two-tailed p value was .065, considered not quite significant. We conclude that the presence of a pituitary incidentaloma can cause partial GHD. After statistical analysis, it was observed that obesity was not the cause of the difference in the peak GH levels. Pituitary incidentalomas are not completely incidental and, if present, should direct the endocrinologist to order an IGF-1, and if low or low normal, then GH stimulation testing should be performed.
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