Plasma Growth Hormone In Patients Research Articles

Effect of Intravenous Administration of Growth Hormone-Releasing Peptide on Plasma Growth Hormone in Patients with Short Stature

Synthetic hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP) is known to have remarkable GH releasing activity in a variety of species, especially in men. In this study, we examined the effects of GHRP (1μg/kg BW, iv) on plasma GH in 41 patients with short stature (29 males and 12 females, aged from 8-28 yrs) due to different causes (one after pituitary adenomectomy, nine with perinatal abnormality, two with Turner syndrome, 28 due to unknown causes), and compared the GH responses to GHRP with those to GHRH, L-dopa and insulin. GHRP did not cause any symptoms after the injection. Among 35 patients who had no organic abnormality at the hypothalamo-pituitary region in MRI, plasma GH rises of more than 7μg/L were observed in 34 patients after GHRP injection, 32 patients after GHRH, 21 patients after L-dopa and 24 patients after insulin-hypoglycemia. The mean±SE peaks of plasma GH were 26.6 ± 2.8 μg/L after GHRP, 24.0 ± 3.11/g/L after GHRH, 7.1±1.1 μg/L after L-dopa and 7.5 ± 1.1 μg/L after insulin. Plasma GH peaks appeared within 45 min after GHRP injection, which was earlier than the time of GH peaks in other provocation tests. On the other hand, GHRH slightly but consistently increased plasma GH levels in short patients with pituitary stalk transsection, whereas GHRP did not. Although the mechanism of this finding remains unclear, other factors may be necessary for GHRP to exert its full activity in GH release.In summary, GHRP increased the plasma GH level in patients with short stature more safely, consistently and quickly than other GH stimulants. The GHRP test will therefore be a useful and practical way to examine the GH secretory reserve in short stature.

Effect of dopamine on plasma growth hormone and prolactin concentrations under anaesthesia.

Five patients with acromegaly and five patients with prolactinoma undergoing general anaesthesia were studied. Concentrations of plasma growth hormone in patients with acromegaly and concentrations of plasma prolactin in patients with prolactinoma were measured before anaesthesia, when 250 mg levodopa was administered orally, and after anaesthesia when dopamine was infused intravenously at a rate of 5 micrograms/kg.min. There was no difference in hormonal (growth hormone or prolactin) response to either treatment in the anaesthetized and the awake states. These findings indicate that the functioning of dopamine receptors in the anterior pituitary is not affected by anaesthesia.

Growth Hormone Hyperresponsiveness to Dopaminergic Stimulation in Huntington’s Chorea

The effect of 3 dopamine (DA) mimetic drugs, i.e. bromocriptine (Bro), apomorphine (Apo) and L-3,4-Dihydroxpenylalanine (L-dopa), was evaluated on plasma growth hormone (GH) levels in 18 patients with Huntington's chorea (HC). 27 Nonobese hospitalized patients were used as controls. Mean baseline GH levels were not altered in patients with HC. Oral administration of Bro (2.5 mg po) or L-dopa (500 mg), or subcutaneous administration of Apo (1.0 mg) resulted in a significantly greater and more prompt (Bro, L-dopa) increase in plasma GH in patients than in controls. These results suggest that presence of an altered dopaminergic regulation of GH secretion in HC.

Plasma growth hormone in patients with chromosomal anomalies.

Plasma growth hormone in patients with chromosomal anomalies.

Stimulation of human-growth-hormone secretion by L-dopa.

The effect of L-dopa, a precursor of Central-nervous-system catecholamines, on growth-hormone secretion was studied in a group of patients with Parkinson's disease undergoing treatment with the drug. Oral doses (0.5 g) caused a significant rise in plasma growth hormone in patients initially starting therapy or on chronic therapy for as long as 11 months. The rise in plasma growth hormone persisted for 120 minutes after the administration of the drug. The L-dopa-induced rise in plasma growth hormone could not be blocked by either oral or intravenous glucose administration. The data suggest that a dopaminergic mechanism in the median eminence or a norepinephrine-sensitive site in the hypothalamus or limbic system may be involved in the regulation of growth-hormone secretion. Furthermore, patients with Parkinson's disease, on L-dopa therapy, appear to be under the influence of elevated plasma growth hormone for a substantial part of the day.