PSAT104 Predicting Response to Growth Hormone Therapy with Pituitary Volume and The Growth Hormone Stimulation Test

BACKGROUND: Patients with diminished growth hormone (GH) secretion are candidates for GH therapy (GHT). The GH stimulation test (GHST) is considered the gold standard for the diagnosis of GH deficiency (GHD), yet its efficacy has been questioned. In this study we explore the GHST and PV's ability to define GHD and determine their individual ability to predict GHT outcomes. SUBJECTS AND METHODS: A database at a Pediatric Endocrinology center was queried for patients aged 6-18 yrs who underwent a GHST, MRI, and GHT between 1/2018 - 1/2021. Patients with a first follow up (FU) between 3 and 9 months were included; of these patients, second FUs were included if they occurred between 9 and 15 months. Patients with relevant comorbidities, those with GHST peak ≥ 10.0 ng/mL, and nonadherent patients were excluded. MRIs were acquired on a Philips 1.5 or 3.0 T scanner (2mm slices) and PV was calculated using the ellipsoid formula (LxWxH/2). PV and height were converted to SDS. Response to treatment was defined as change in height SDS over the assessed time interval. A multiple linear regression was utilized to analyze the response to GHT relative to peak GH and PV, with initial height and age at stimulation included as covariates. The relationship between peak GH and PV SDS was analyzed with a Pearson correlation RESULTS: The first FU ranged between 3.1 and 8.9 months, and the second FU ranged between 9.0 and 14.9 months. 145 patients had one FU, and 83 patients had two FUs. Peak GH and PV SDS were not correlated (r=0.03). Patients who were relatively shorter for their age and gender at stimulation had higher growth rates in the first interval, but not in the second interval. Both PV and peak GH provided information about response to GHT. PV SDS negatively predicted the relative growth response to treatment in the first interval (slope=-0.03, p=0.048). However, PV only explained 3.7% of variation in growth. PV SDS was not a useful predictor of response in the second interval (slope=-0.01, p=0.693). Peak GH was a predictor of response to GHT in the first interval only after accounting for age at stimulation and initial height (slope=-0.01, p=0.032; r2=0.01). Peak GH was a predictor of response in the second interval (slope=-0.02, p=0.040), explaining 5.1% of the variation in growth. CONCLUSION: Since peak GH and PV were not correlated, they likely reflect different physiological processes. PV and peak GH both provide information about response to GHT, so they should both be utilized to determine eligibility for GHT. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.