We have shown that short children have significantly reduced pituitary volume (PV)s and have speculated PV as a cause for diminished chronic growth hormone (GH) secretion and poor growth. In this study, we further elucidate the role of PV in the etiology of short stature (SS) in a larger cohort of siblings (SBs).The database of a Peds Endo Center between 2013-21 was queried for siblings with SS who underwent a GH Stimulation test (GHST) and MRI evaluation. Their results were compared with normal controls (NCs) as previously reported. 129 SBs of 60 families were compared to 170 NCs. SBs were divided into 3 groups (GPs). GP1 (n=79) consisted of families with only GHD. GP2 (n=12) contained families with only ISS SBs. GP3 (n=38) comprised families with mixed GHD and ISS. SBs 11 yrs were considered prepubertal (prePB) and pubertal (PB), RSP. The mean (MN) and median (MD) age for both prePB and PB SBs were significantly different (p 0.05). The 32 PB patients in GP3 had a mean PV of 316.17± 197.53 mm3, which was significantly different from that of the PB NCs of 424.6 ± 138.4 mm3 (p Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.