Evaluation of pituitary function in children using growth hormone secretagogues.

We have devised a diagnostic test to directly evaluate pituitary secretory potential, and also to identify the most appropriate therapy for slow growing children. The test compares responses to GH releasing hormone (GHRH) and GH releasing peptides or their non-peptidyl mimics (GHRP) administered sequentially and in combination. Since they are functional complements, robust GH secretion in response to GHRH or GHRP could be interpreted as representing adequate endogenous GHRP or GHRH, respectively. Alternatively, assuming that all pituitary cellular and molecular elements for GHRH- and GHRP-mediated GH secretion are functional, a poor response to either GH secretagogue administered individually could represent inadequacy of its endogenous complement. The integrity of functional pituitary elements could be differentiated from inadequate endogenous complement by administering both GH secretagogues simultaneously. Based upon this hypothesis, the proposed pituitary function diagnostic scheme could be used to test for endogenous GH secretagogue adequacy, as well as pituitary secretory capacity. The data resulting from application of these principles would allow appropriate selection of therapeutic entities, ranging from GHRH or GHRP administered separately or in combination, or alternatively, recombinant GH for those patients lacking a pituitary mechanism for GH production and/or secretion.