Factors influencing the growth hormone peak and plasma insulin-like growth factor I in young adults with pituitary stalk interruption syndrome

Abstract

Abstract Background The diagnostic criteria for growth hormone (GH) deficiency (GHD) in adolescents and young adults are not yet clearly established. We evaluated the factors influencing the GH peak and plasma insulin-like growth factor (IGF) I in order to determine the cut-off limits for the diagnosis of GHD during the transition period. Methods 21 patients treated for GHD due to pituitary stalk interruption syndrome at 5.7 ± 4.1 years were reevaluated at 16.0 ± 1.8 years, 0.6 ± 0.6 years after the end of GH treatment. Group 1 had isolated GHD (n = 9) and group 2 had multiple pituitary deficiencies (n = 12), including deficiencies of thyroid stimulating (n = 12), adrenocorticotropin (n = 8) and gonadotropin (n = 9) hormones. Results At diagnosis, group 1 had a greater pituitary height (2.8 ± 1.2 vs 1.6 ± 1.1 mm, P = 0.03) and GH peak (3.8 ± 1.9 vs 1.6 ± 1.5 ng/ml, P < 0.02) than did group 2. At last evaluation, group 1 had greater GH peak (3.9 ± 1.9 vs 0.2 ± 0.4 ng/ml, P = 0.0001) and plasma IGF I (211 ± 88 vs 78 ± 69 ng/ml, P < 0.002) than did group 2. No group 1 and 9 group 2 patients had an undetectable GH peak, while the 3 others had GH peak below 1 ng/ml. The GH peak decreased between diagnosis and last evaluation only in group 2 (P < 0.008). Conclusion The GH peak response to pharmacological stimulation and the plasma IGF I concentration in young adults with GHD of childhood onset depend on the presence of additional pituitary deficiencies, reflecting a more severe defect of the hypothalamic-pituitary axis. The sex steroids cannot increase the IGF I if the GH secretion is zero.