A Boy without Growth Hormone is Growing Normally

This is a 12 year and 5 month old prepubertal boy, who was followed from the neonatal period because of tertiary hypothyroidism. Endocrinological examinations were performed on three occasions. All the data revealed growth hormone (GH) deficiency and hypothyroidism. GH responses to insulin, arginine and GH-releasing factor (GRF), and the nocturnal GH secretion test, were low and sometimes undetectable. In addition, the serum insulin-like growth factor I (IGF-I) values were always low. Thyroid-stimulating hormone (TSH) responses to the TSH-releasing hormone (TRH) provocation test showed a tertiary hypothyroidism pattern. The values of luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone were in the pre-pubertal stage and prolactin was in the normal range. Magnetic resonance (MR) imaging showed a small pituitary with stalk interruption, in spite of normal delivery. With the use of levothyroxine, growth has been maintained in the range between -1 standard deviation (SD) and -2 SD. In this case GH and IGF-I are not indispensable for maintaining physical growth, and the abnormal pituitary imaging is not caused by perinatal insult. Further detailed investigations, including a search for some growth-promoting bioactivity other than GH, are needed to elucidate the mechanism of this patient's growth.