Aims: To report false-negative normal growth hormone (GH) peak response in patients with ectopic posterior pituitary gland (EPP) identified with a simplified magnetic resonance imaging (FAST1-MRI). Methods: We analyzed 75 EPP patients with short stature and reduced growth velocity. Sagittal-T1 imaging (thickness: 2 mm and gap: 0.2 mm) without gadolinium administration was used. A GH peak of ≥5 ng/ml after clonidine or insulin stimulation was considered normal. Results: Normal GH response was observed in 15 of 75 (20%) patients [mean (SDS) peak = 8.2 (4.1) ng/ml]. Age at diagnosis [6.5 (3.0) years vs. 7.8 (4.1) years], gender (10 males/5 females vs. 44 males/16 females), pubertal stage (14 prepubertal/1 pubertal vs. 51 prepubertal/7 pubertal), and target height [-0.4 (0.6) vs. -0.4 (0.9)] were recorded. The perinatal history did not differ between responsive and nonresponsive patients. There was a trend to more frequent multiple hormone deficiency in nonresponsive when compared with responsive patients [3/15 (20%) and 31/60 (51.7%), respectively (p = 0.055)]. Height at diagnosis was lower in nonresponsive patients (p = 0.042). No significant difference in the IGF1 levels (p = 0.598) was observed between the groups. Conclusion: Normal GH values after stimulation tests do not exclude EPP-associated GH deficiency. A simplified fast acquisition sagittal-T1 MRI protocol investigation included at the initial diagnostic approach is able to prevent misdiagnosis of GH deficiency in patients with short stature.