RESUMOIntrodução: A associação de síndrome do cromossomo 18 em anel com deficiência de hormônio de crescimento (DGH) é muito rara, com apenas dois relatos na literatura. Relato do caso: Paciente feminina, negra, 1 ano de idade, encaminhada para investigação de crises de hipoglicemia desde os 6 meses, acompanhadas de crise convulsiva. Apresentava atraso do desenvolvimento neuropsicomotor e erro alimentar. Ao exame físico, criança desnutrida (escores z peso/idade de -6,95 e estatura/idade de -5,05), fenda palatina, prega epicântica e hipotonia generalizada. O diagnóstico de DGH foi feito em vigência de hipoglicemia e iniciado o tratamento com somatropina 0,1 U/kg aos 16 meses de idade. A RM do crânio evidenciou neuro-hipófise ectópica. O hipotireoidismo foi diagnosticado com 1 ano e 7 meses, sendo adicionada levotiroxina ao tratamento. O cariótipo 46XX r (18) The association of 18-ring chromosome syndrome and growth hormone deficiency (GHD) is extremely rare, with only two reports in the literature. Case report: A one year-old, non-white female was referred due to hypoglycemic seizures. She had developmental delay and poor nutrition. Her physical examination was significant for a weight Z score of -6.95, height Z score of -5,05, cleft palate, epicanthic folds and generalized hypotony. Karyotype was 46XX r(18) (p11,2 -q.23) -18 ring chromosome syndrome, the MRI showed an ectopic neurohypophysis. The diagnosis GHD was made due to low GH levels during spontaneous severe hypoglycemia at the age of 16 months. She was started on hGH 0.1 U/kg/day. Three months later, TSH deficiency was diagnosed and Lthyroxin therapy was started. During hGH replacement the hypoglycemic events stopped but after 3 years of hGH therapy, she did not improve growth velocity. Discussion: We were unable to find any report of GHD and hypothyroidism associated with the 18-ring chromosome syndrome. Children with 18-ring chromosome should undergo investigation of GHD. In our child with 18-ring syndrome the hGH therapy did not improve growth velocity.