Growth hormone responses to propranolol-glucagon stimulation: a comparison with other tests of growth hormone reserve

Glucagon stimulates GH secretion after intramuscular but not intravenous administration. Evidence against the assumption that glucagon per se has a GH-releasing activity

In order to verify the true GH-releasing effect of glucagon and to explain the mechanism underlying this effect, we studied the effect of glucagon (GLU, 1 mg) administered either iv or im on both basal and GHRH (1 microgram/kg)-induced GH rise in 48 normal short children and adolescents. Moreover, the in vitro effect of GLU on rat anterior pituitary cells was studied. Intravenous administration of GLU induced no significant GH rise. On the other hand, im GLU administration induced a clear-cut GH increase (mean +/- SE GH peak after GLU vs placebo = 25.7 +/- 3.9 vs 10.1 +/- 3.6 micrograms/L, p < 0.01). Intravenous administration of GLU failed to modify the GHRH-induced GH rise either when coadministered with the neurohormone (35.2 +/- 4.1 vs 34.1 +/- 6.0 micrograms/L) or when given 60 min earlier (20.2 +/- 5.8 vs 21.1 +/- 8.3 micrograms/L). Differently from iv GLU, im GLU strikingly potentiated the GH response to GHRH given 90 min later (57.5 +/- 6.3 vs 24.7 +/- 9.1 micrograms/L, p < 0.01). Mean plasma glucose levels increased 30 min after GLU, administered either iv or im, and returned to basal levels 60 min later. GH secretion from dispersed rat pituitary cells was unaffected by incubation with GLU (10(-10)-10(-4) mol/L). Incubation of the cells with 10(-7) mol/L GHRH induced instead a clear-cut stimulation of GH release. In conclusion, our data demonstrate that glucagon per se has not GH-releasing activity as indicated by its uneffectiveness to release GH in vitro and after intravenous administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial occurrence of growth hormone deficiency and primary hypothyroidism

We examined endocrine function in three male siblings with growth hormone (GH) deficiency and primary hypothyroidism. Low GH responses to various provocative tests were revealed in all three. Exaggerated thyrotropin (TSH) responses to thyrotropin-releasing hormone increased basal TSH levels, and low free thyroxine levels were also found in all three. Additionally, a low testosterone response to human chorionic gonadotropin and low gonadotropin responses to luteinizing hormone-releasing hormone were noted in the youngest sibling. Skull X-ray films, computerized tomography and magnetic resonance imaging revealed no abnormalities of the pituitary gland or sella turcica. The GH gene was intact in all of the children and their parents. We diagnosed all siblings as having GH deficiency and primary hypothyroidism. This is the first report of familial occurrence of GH deficiency and primary hypothyroidism.

Evidence of polyglandular involvement in Niemann-Pick disease type B

We report a girl with Niemann-Pick disease type B in whom short stature was recorded over a long period. Association of short stature with the presence of a polyglandular involvement in this patient is discussed.

Intramuscular glucagon as a provocative stimulus for the assessment of pituitary function: growth hormone and cortisol responses

The response of plasma growth hormone and cortisol to the intramuscular injection of 1 mg glucagon was used to assess anterior pituitary function in a group of 97 normal subjects (23 men, 74 women). Ninety-three subjects (96%) responded with a peak GH of at least 8 ng/mL, and 89 (92%) had either a peak cortisol of at least 500 nmol/L (18 micrograms/dL) or a maximal increment in plasma cortisol of at least 250 nmol/L (9 micrograms/dL) above the baseline. In 12 subjects, a second test showed that the responses were reproducible. A greater proportion of subjects over the age of 50 failed to achieve a peak GH of 10 ng/mL (7 of 20, 35%) compared to those who were either under 30 (1 of 37, 2.7%) or between 30 and 50 (4 of 40, 10%) (chi 2 = 12.85, P less than .005). GH responses were not affected by sex or elevation of the basal level of GH. In contrast, cortisol responses were smaller in men and in individuals with high basal cortisol levels but were not affected by age. Mild nausea in approximately 30% of subjects (29 of 97), and transient vomiting and retching in approximately 10% (10 of 97) were the only side effects that were noted. Glucagon is therefore a safe and reliable alternative to insulin-induced hypoglycemia for the assessment of both somatotrophic and corticotrophic function.

The endocrine spectrum of septo-optic dysplasia

Six children with septo-optic dysplasia were evaluated at the Children's Hospital of Philadelphia. There was a common history of young, nulliparous mothers. The clinical presentation of these children differed according to age of presentation and was a function of the degree and type of hypothalamic-pituitary and ophthalmologic impairment. Endocrine evaluation revealed four of six children to be growth hormone deficient, four of six to have hypothalamic hypothyroidism, and two of four to have elevated prolactin levels. One of the patients demonstrated adrenocorticotropic hormone deficiency, and one had diabetes insipidus. Neuroanatomic findings in the children were variable, but, in general, the rare syndrome did not carry as grave a morbidity as had been reported previously. Our data support a high degree of hypothalamic impairment in septo-optic dysplasia.

Betaxolol and propranolol in glucagon stimulation of growth hormone

Both betaxolol and propranolol, beta blockers with different pharmacological properties, increase the reliability of somatotropic testing with glucagon. The combination of glucagon and betaxolol, however, is much better tolerated than that of glucagon and propranolol. The use of a beta 1 cardioselective adrenoceptor block for growth hormone testing is recommended.

Hypothalamic-pituitary functions in patients with idiopathic pituitary dwarfism. Further evidence for hypophysiotropic human deficiencies

Somatotropic, thyrotropic, gonadotropic and corticotropic functions in 10 patients with idiopathic hypopituitary dwarfism (IH) were investigated. The patients were divided into two groups: Group I (5 patients) had normal plasma T4 levels, and Group II (5 patients) had T4 levels of less than 4.6 microgram/dl. In Group I three cases had isolated growth hormone (GH) deficiency and two cases had GH and gonadotropin (Gn) deficiencies; in Group II the 5 cases showed multiple anterior pituitary hormone deficiencies. In Group II, the plasma thyroid stimulating hormone (TSH) was 4.1-9.4 muU/ml and the response to thyrotropin releasing hormone (TRH) was greatly delayed and prolonged, with a maximum after 120 min instead of 15 min. The basal prolactin (PRL) level in Group II was 12-31 ng/ml, which was significantly higher than normal (P less than 0.001). In 4 cases in Group II, the plasma cortisol level increased 120 min after the infusion of lysine-vasopressin, whereas oral administration of metyrapone and hypoglycemia induced by insulin did not increase the plasma cortisol levels. From these findings it is concluded that hypothalamic lesions caused the pituitary hormone deficiencies in 4 Group II cases, and Group I may tentatively be differentiated from Group II by T4 determinations.

Familial hypopituitarism with large sella turcica

We studied endocrine function in three siblings with short stature and enlargement of the sella turcica. Sellar volumes were 5.9, 3.7 and 4.0 standard deviations above age-specific means. Computed tomography or pneumoencephalography showed full sellae without suprasellar extension. Basal thyrotropin levels were low despite hypothyroidism and increments were less than 3 micromicron per milliliter after thyrotropin-releasing hormone injection. Stimulated growth hormone levels were less than 5 ng per milliliter, declining to less than 2 ng per milliliter after thyroxine treatment. Both thyroxine and growth hormone treatments were required for rapid growth. Impaired thyrotropin responses to thyrotropin-releasing hormone distinguish these patients from most cases of idiopathic or familial deficiency of thyrotropin and growth hormone. Persistent deficiency of growth hormone during thyroxine treatment indicates that the defects is not limited to thyrotropin structure or release. The findings are compatible with either familial neoplasia of the anterior pituitary or a regulatory defect promoting anterior pituitary-cell hyperplasia and inhibiting thyrotropin and growth hormone release.

Comparative HGH response to i.v. glucagon and i.v. arginine stimulation tests in children and adolescents

Thirty-seven children and adolescents of several diagnostic entitites (constitutional growth retardation, diabetes mellitus and pituitary insufficiency) were tested with an i.v. bolus injection of glucagon for plasma human growth hormone (HGH) response. Most of the subjects were also tested for the same purpose by the arginine stimulation test, and the data were compared. It was found that i.v. glucagon is a potent stimulus of human growth hormone release. The HGH is released in two peaks, the first one occuring within 30 min, most probably by a direct effect. The second peak occurs after 120 min, most probably as a secondary effect caused by the drop in blood glucose after its initial rise, which is induced by glucagon. The peak concentrations of HGH induced by glucagon, were very similar to those provoked by i.v. arginine in the same subjects.