Growth retardation can be due to inadequate growth hormone secretion or lack of biological response to Us effects. The clinical picture is quite similar in both conditions. Growth hormone exerts its biological effects through cellular receptors which, if absenl, can lead to growth retardation. We present a 14 year 7 month old boy with extreme short stalure [heighl 95 cmj, centripetal obesity, small hands and feets, miaopenis, and immature facies, which suggested growth hormone deficiency. His serum growth hormone concentrations were elevated, and his somatomedin-C was decreased. The boy was treated with growth hormone and he did not show any biochemical or clinical response, suggesting that he has growth hormone resistance.

ResumenEn una nina con hipotiroidismo primario debido a tiroides sublingual y talla ba[a desde los dos ahos de edad, la resonancia magnetico mostro auTienlo del tamaiio de la hipofisis sugerente de rnacroadenoma, que despues de una prueba terapeutica con hormona tiroidea recupero el aspecto normal. El hipotiroidismo primario cronico puede producir aumenta de volumen hipofisiario indistinguible del causado por un rnacroadenoma en los examenes por imagenes. El tratamiento con horrnona tiroidea permite el diagnosfico direrencial entre ambas entidades.(Palabras clave: hipotiroidismo primario, pseudo rnacroadenoma htoofisisario, talla baja.) Primary hipothyroidism simulating pituitary macroadenoma differential diagnosis among both conditions.(Key words: hipothyroidism, pituitary neoplasm, short stature.) Perez P. y cols. Revista Chilena de PedlatrfaJulio-Agosto 1998