Comparison of growth hormone releasing hormone therapy and growth hormone therapy in growth hormone deficiency

[Treatment of growth hormone deficiencies with growth hormone releasing hormone. Current status and perspectives]

Results of clinical trials performed with human hypothalamic growth hormone releasing factor (GRF) are conflicting, but rather disappointing for most of them. Pulsatile administration of GRF has been found to increase growth hormone secretion as well as growth velocity, but is not convenient for practical use. All other routes and rhythms of administration lead only to sub-optimal results, and generally does not seem to procure an appropriate GRF bio-availability. Improvements are possible, particularly the development of agonists and new galenic forms with sustained release. Therapeutic approach with hexapeptides, or hexapeptides analogs, looks promising, but could be more complementary than competitive.

The therapeutic use of growth-hormone-releasing hormone

As a significant number of children with growth hormone deficiency have been shown to be able to respond to GHRH with a rise in serum growth hormone (GH) levels, GHRH has been used to treat such children with varying success. GHRH has been given subcutaneously (SC) in GH deficient children to improve growth in dose frequencies of daily, twice daily, three-hourly overnight or three-hourly throughout the day. The dosages of GHRH used have been wide ranging, varying from 4 micrograms/kg/day to 50 micrograms/kg/day. Continuous infusion of GHRH has been shown to augment GH secretion in normal adults and GH deficient children without evidence of desensitization of the somatotrophs. Continuous SC infusion of GHRH has been shown to promote growth in short slowly growing children. Poor growth response to GHRH has been reported by some authors using daily SC injection while others reported significant growth acceleration in 42-87% of GH deficient children treated using different GHRH regimens. Although GH treatment in GH-deficient children results in more consistent growth acceleration, comparable growth response can be seen in some children treated with GHRH. The optimal mode of GHRH therapy remains to be determined, but it would appear that the growth response is dependent on the dose used and possibly on the frequency of administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Long term growth hormone (GH)-releasing hormone and biosynthetic GH therapy in GH-deficient children: comparison of therapeutic effectiveness

Twenty-five GH-deficient children were treated with GHRH (1-44), once daily sc for 6-24 months. At the 6th month of therapy, 40% of our patients showed a catch-up growth (responders), while the remaining 60% did not (nonresponders). No differences in auxological and biological variables at inclusion were found between the two groups. However, integrated GH secretion elicited by iv GHRH at inclusion was significantly (p less than 0.025) higher in responders than in non responders. During GHRH therapy, no significant increase in IGF 1/SmC was found in both groups. In all patients treatment was discontinued after 6-24 months, when its effect on growth rate failed. After a wash-out period of at least 6 months, patients were submitted to biosynthetic GH therapy. After 6 months of GH treatment a significant catch-up growth was found in both responder and non-responder children. Although the majority of GH-deficient children have hypothalamic rather than pituitary dysfunction, GHRH therapy is found to be less effective than GH treatment. Other methods of GHRH administration are worth investigating.

Diagnostic value of growth hormone-releasing hormone tests in short children

The growth hormone-releasing hormone (GHRH) test was applied to more than 230 children. Twenty-five out of 61 patients with proven growth hormone (GH) deficiency responded to GHRH with a GH increase of greater than 10 ng/ml. In most of the patients with idiopathic GH deficiency, a priming procedure using daily injections of GHRH improved the secretory response to GHRH. Nearly all children with familial shortness of stature showed a prompt increase in GH levels, with a mean peak level of 34.9 ng/ml (range 0.5-144 ng/ml). A second test was performed in five children with familial short stature because of failure to respond to the first test. Children with constitutional delay of growth and development did not differ in their GH response from patients with familial shortness of stature. Ten girls with Ullrich-Turner's syndrome responded with a mean increase of 22 ng/ml GH (range 10.1-34.0 ng/ml). Therapy with glucocorticoids, as well as endogenous hypersecretion of cortisol, suppressed the responsiveness of the pituitary gland to GHRH. Suppression was also observed following a single dose of dexamethasone during the steroid-suppression test in eight obese children. Low responsiveness of the pituitary gland was also seen in patients with thalassaemia and transfusion-induced haemosiderosis. It is concluded that it is not possible to detect GH deficiency with a single GHRH test. A full endocrinological evaluation is necessary to prove the diagnosis.