Damjanović, Svetozar (7003775804)Svetozar (7003775804)DamjanovićPopović, Vera (35451450900)Vera (35451450900)PopovićPetakov, Milan (7003976693)Milan (7003976693)PetakovDjurović, Marina (6603668923)Marina (6603668923)DjurovićDieguez, Carlos (58502650200)Carlos (58502650200)DieguezCasanueva, Felipe F. (7103087629)Felipe F. (7103087629)Casanueva2025-06-122025-06-121996https://doi.org/10.1515/JPEM.1996.9.5.549https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029988256&doi=10.1515%2fJPEM.1996.9.5.549&partnerID=40&md5=6c3e1d2588abd3887d94e8077388db39https://remedy.med.bg.ac.rs/handle/123456789/1608GH secretion after growth hormone-releasing hormone (GHRH), growth hormone releasing peptide-6 (GHRP-6) and after combined administration of both peptides was studied in a patient with lactotrope and thyrotrope hyperplasia due to primary hypothyroidism. Pituitary pseudotumor disappeared after thyroid hormone replacement; this was evidenced by magnetic resonance imaging (NMR). There was no difference between areas under the curve (AUC(0-120min)) during GHRH test before and after thyroid hormone replacement (136.5 vs 129.0 μg/l min). Maximal GH increases over basal values (ΔGH) did not change (1.5 and 1.9 μg/l) GH secretion induced by GHRP-6 increased after treatment (AUC(0-120min) 197.2 vs 650.4 μg/l min). ΔGH increments were 4.0 and 18.3 μg/l before and after therapy respectively, When the peptides were administered together a synergistic effect on GH secretion was observed but GH release was much more powerful after pituitary pseudotumor disappearance (AUC(0-120min) 1043.2 vs 2046.7 μg/l min). This was accompanied by increased ΔGH (22.7 vs 35.5 μg/l). The synergic action of peptides normalized in euthyroid condition and after the resolution of pituitary pseudotumor mainly due to improved GB[ response to GHRP-6. Blunted response of GH to GHRP-6 and GHRP-6 plus GHRH were in part due to known effects of hypothyroidism on GH secretion. Hypothalamopituitary disconnection and/or decrease in the synthesis of an unknown factor in the hypothalamus which mediates the effects of GHRP-6 may have participated in the GH responsiveness of this patient, This case adds to in vivo evidence that GHRP-6 operates through a non-GHRH dependent mechanism.GHRHGHRP-6Growth hormonePituitary thyrotrope and lactotrope hyperplasiaPrimary hypothyroidism