The effects of thyrotropin-releasing hormone and luteinizing hormone-releasing hormone on growth hormone release in patients with homozygous beta-thalassaemia

Growth hormone secretion in polytransfused prepubertal patients with homozygous beta-thalassemia. Effect of long-term recombinant GH (recGH) therapy

Growth was monitored in 133 male and 150 female North Sardinian prepubertal patients with homozygous beta-thalassemia in order to ascertain the incidence of GH deficiency (GHD) and the effects of long-term recombinant GH (recGH) treatment on growth velocity and bone maturation. A significant reduction in growth velocity and a fall in IGF-I levels was observed in 19 male and 16 female patients (12.3%). Their peak GH responses to GHRH (5.45+/-0.78 and 4.99+/-0.86 ng/ml) and clonidine administration (4.21+/-0.32 and 4.15+/-0.27 ng/ml in males and females, respectively) were markedly reduced with respect to control subjects (p<0.01). No statistically significant correlation was found between chronological age, number of blood units received, plasma ferritin levels and plasma IGF-I levels as well as with peak GH response to stimulation. Thalassemic patients with GHD had plasma ferritin levels (1382.44+/-160.34 and 1255.23+/-139.81 ng/ml in males and females, respectively) significantly lower than those recorded in the other patients (2848.94+/-283.61 and 3077.82+/-220.51 ng/ml). Patients with GHD were treated with recGH for an average period of 59 months (range 26-124). Treatment was able to restore growth and to increase significantly plasma IGF-I levels. Growth velocity at the end of the first yr of treatment was 6.78+/-1.21 and 6.11+/-0.85 cm/yr in males and females, respectively. Growth velocity values and plasma IGF-I levels remained significantly higher than basal values throughout the period of treatment. However, treatment was unable to normalize bone maturation since bone age values were always reduced with respect to chronological age. No incidence of side effects was observed. These data indicate that GHD, when present, is one but not the sole cause of delayed bone maturation and height deficiency in thalassemia.

Evaluation of growth hormone in thalassaemic boys with failed puberty: spontaneous versus provocative test

Growth hormone (GH) secretion was determined by evaluating ultradian GH profiles for 12 h and GH responses to insulin stimulated hypoglycaemia (ITT) in 28 stunted boys with beta-thalassaemia major aged 15.2-17.4 years, who presented with pubertal failure (FP). Healthy non thalassaemia prepubertal boys (n = 10) aged 7.5-8.8 years, were studied as controls. All patients had normal responses to ITT with peak GH levels > or = 15 mU/l. Basal GH concentrations (mean +/- sem) (1.65 +/- 0.03 mU/l vs 2.58 +/- 0.27 mU/l; P < 0.05) and the stimulated GH responses (peak GH = 15.4 +/- 0.20 mU/l vs 21.08 +/- 0.78 mU/l; P < 0.001) were significantly lower in the patients with failed puberty than in the controls, indicating that the FP patients had diminished GH reserve and secretory capacity. Moreover, all the GH peak parameters including the maximum spontaneous concentrations (MX-GH) and the area under the GH curve (AUC) were significantly lower in the thalassaemic patients than in the controls (MX-GH = 5.2 +/- 0.21 mU/l vs 20.42 +/- 0.14 mU/l; P < 0.001; AUCb = 421.22 +/- 4.31 mU/l vs 712.20 +/- 3.42 mU/l; P < 0.001). These observations suggest that the thalassaemic patients had endogenous neurosecretory GH deficiency (GHND). Priming with sex steroid did not cause any improvement in the spontaneous or stimulated GH secretory patterns in thalassaemic patients. It was noteworthy that in neither the patients nor the control subjects, was there a significant correlation between the maximum stimulated and the MX-GH concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Inappropriate growth-hormone (GH) response to thyrotropin-releasing hormone (TRH) occurs infrequently in well-regulated diabetes mellitus

We randomly administered thyrotropin-releasing hormone (200 micrograms, as an i.v. bolus) or control saline (in isovolumic amount) to 30 male diabetic subjects (23 IDDM, 7 NIDDM) in fair metabolic control (HbA1 9.7 +/- 0.3%, means +/- SEM) and to 12 healthy male controls on two different mornings. While GH in the basal state was similar in IDDM, NIDDM and normal subjects, TRH administration evoked a significant GH release only in a single IDDM individual. The only GH-responder to TRH was a newly-diagnosed (two weeks) IDDM patient, still with a high glycated hemoglobin level (HbA1 11.1%), despite normal plasma glucose levels. Saline infusion did not affect GH concentrations either in normals or in diabetics. Exaggerated GH responses to TRH are uncommon in diabetic patients in good metabolic conditions.

Thyrotropin-releasing hormone enhances event-related brain potentials and growth hormone release in man

Changes in contingent negative variation (CNV), a brain-evoked potential related in arousal, as well as in serum triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), prolactin (PRL), cortisol and growth hormone (GH) levels were recorded in 12 male volunteers receiving either thyrotropin-releasing hormone (TRH) or saline infusion. Only during TRH administration an increase in CNV (P less than 0.02) and, 30 min later, in GH (P less than 0.05) occurred; thyroid hormones and PRL increased as well, in the absence of any correlation with CNV areas. Cortisol was not affected by TRH. As dopamine (DA) agonistic drugs notoriously increase both CNV areas and GH levels and experimental evidence for prodopaminergic properties of TRH has accumulated in animal models, a possible explanation of the results here presented might be the activation of DA pathways by TRH also in the human.

Arginine induced growth hormone (hGH) response and paradoxical hGH secretion stimulated by TRH in diabetes mellitus

Growth hormone (hGH) reserve following arginine administration and the paradoxical hGH response to thyrotropin-releasing hormone (TRH) were studied in 30 diabetics without evidence of vascular complications. The diabetics were divided into 4 groups according to the type of their disease and to the metabolic condition within the IDDM group (insulin-dependent: IDDM, in acceptable response and in poor metabolic control; non-insulin-dependent: NIDDM, and juvenile diabetics not requiring insulin at least for two years after diagnosing their disease: NIDDY). The results were compared with controls of identical age and normal weight. A paradoxical hGH response to TRH stimulation was found only in IDDM patients in poor metabolic control. In this group the hGH reserve revealed by arginine was significantly larger than in the others. It was shown that the induced hGH release was independent of the sex distribution of the groups and of the basal hGH values. Magnitude of the hGH reserve and appearance of the paradoxical hGH response were not necessarily correlated but the substantial reserve was frequently associated with a paradoxical response. It can be assumed that the unfavorable metabolic condition is of decisive importance in giving rise to these anomalies. Our observations seem to confirm the need for good metabolic control if the pathological hGH secretion in diabetics is to be prevented.

Effects of intravenous TRH on growth hormone and cortisol serum levels in children and adolescents with insulin dependent diabetes mellitus

The effects of an iv thyrotropin releasing hormone (TRH) bolus on serum growth hormone (GH) and cortisol levels were evaluated in 59 children and adolescents with insulin dependent diabetes mellitus (IDDM) and in 24 healthy, age-matched control subjects. In the IDDM group GH baseline levels sharply rose within 30 min after TRH and successively normalized. On the contrary, TRH injection failed to affect GH serum concentrations in the control group. The GH increase after TRH in IDDM patients was positively correlated to age, but unrelated to other variables, such as sex, pubertal stage, duration of disease, glycemia, glycosylated hemoglobin, thyrotropin and T4 concentrations. Twenty-one out of 59 diabetics and only 1/24 controls exhibited a paradoxical GH response to TRH, arbitrarily defined as a precocious increase (within 30 min), of more than 100% with respect to the baseline value, associated with a GH peak greater than 10 ng/ml. Eighteen IDDM patients underwent a second TRH test 12 to 24 months later and substantially exhibited the same GH pattern documented the first time. The mechanism responsible for such anomalous GH responsiveness to TRH in IDDM is unclear. However, it cannot be attributed to a nonspecific stress reaction, as proven by the lack of a concomitant increase of cortisol serum levels in the same subjects.