Endocrine Abstracts

Introduction: Hypothalamus or pituitary disorders frequently cause hypopituitarism. Diagnosing deficits of anterior pituitary hormones is important to manage metabolic impairments induced by hypopituitarism. Provocative tests including TRH, LHRH, CRH and GHRP-2 to diagnose hypopituitarism are recommended in Japan, however, the cut-off values in those tests are not adjusted for age, body mass index (BMI) or estimated glomerular filtration rate (eGFR). We retrospectively evaluated effects of age, obesity and renal function on the results of pituitary function tests in patients with hypothalamus or pituitary disorders.

Methods: In this retrospective study, patients with non-functioning pituitary tumor without history of pituitary surgery who admitted and received GHRP-2 test from 2013 until 2016. We evaluated an effect of age, BMI and eGFR on their pituitary functions. To evaluate pituitary function, TRH, LHRH and CRH combination test and GHRP-2 test were performed.

Results: We identified 116 patients who received GHRP-2 test, of which 90 (78%) were non-functioning pituitary adenoma and 17 (15%) were Rathke’s cyst. Of the patients, 111 (96%) received TRH and LHRH test, and 112 (97%) received CRH test in addition to GHRP-2 test. Logarithm of peak serum GH level after GHRP-2 was significantly correlated with BMI (r=−0.37, P<0.001). Serum IGF-1 level was significantly correlated with age (r=−0.518, P<0.001) and eGFR (r=0.19, P=0.037). In multiple regression analysis, age was the only independent variable predicting serum IGF-1 level. Not serum free T4 but free T3 level was significantly correlated with age (r=−0.20, P=0.031) and eGFR (r=0.33, P<0.001). In multiple regression analysis, eGFR was the only independent variable predicting serum free T3 level. Serum TSH level was significantly correlated with age (r=0.19, P=0.041) and eGFR (r=−0.21, P=0.024). In multiple regression analysis, eGFR was the only independent variable predicting serum TSH level. In only men, serum LH level significantly correlated with eGFR (r=−0.34, P=0.009). Plasma ACTH and cortisol levels and their peak levels after CRH were not significantly correlated with age, BMI or eGFR, respectively.

Conclusion: When we diagnose hypopituitarism, we have to recognize that thyroid and gonadal functions might be altered by renal insufficiency and GH response to GHRP-2 might be altered by obesity.