Enhanced hGH pituitary secretion rate associated with somatomedin deficiency as manifested in Laron type dwarfism (LTD)

Abstract

In 3 patients with LTD and 8 normal subjects the following parameters were determined: Integrated 24h hGH concentration (IC-hGH) was elevated in the 2 teenager LTD females and at the upper limit of normal in the young LTD male. The metabolic clearance rate (MCR) was lower in the 2 LTD patients studied than in normal subjects, as in patients with hGH deficiency. The production rate (PR) was elevated in the girl (within the range of acromegaly) whereas in the young man it was only slightly elevated. All 3 LTD patients showed secretory 24h patterns having more frequent and greater fluctuations than in normals. In view of recent findings that the primary defect in LTD is an inability of liver receptors to bind hGH, causing a lack of somatomedin (SM), it is suggested that the enhancement and irregularity of hGH secretion in LTD is due to a dual mechanism, both pathways being related to SM deficiency: 1) lack of negative feedback on pituitary hGH and possibly on GH-RH; 2) lack of stimulating effect on somatostatin secretion.