Study on dioxan separation in the radioimmunoassay of human growth hormone, human chorionic gonadotrophin, adrenocorticotrophic hormone, and insulin

The dioxan precipitation for separating free from antibody-bound hormone in a radioimmunoassay has been applied to human chorionic gonadotrophin (HCG), human growth hormone (HGH), adrenocorticotrophic hormone (ACTH), and insulin and compared with the charcoal-dextran system of separation. The dioxan separation depends on protein concentration. The behaviour of damaged labelled hormone is difficult to assess. Completeness of separation has to be tested in antigen excess. The optimum conditions must be carefully studied for each hormone.

Experience with insulin-induced hypoglycemia as a provocative test for growth hormone and cortisol secretion in children

Insulin-induced hypoglycemia has been used in 109 children with a variety of disorders to assess the hypothalamo-pituitary adrenal axis.The patients were divided into 3 groups: (1) patients with growth retardation and with various disorders where an involvement of the hypothalamo-pituitary region was suspected; (2) obese patients; (3) specific syndromes: spontaneous hypoglycemia, anorexia nervosa, Turner’s syndrome, craniopharyngioma. Glucose, free fatty acids, cortisol and growth hormone were measured before injection of insulin, and at 20-min-intervals thereafter for a period of 2–4 h. The findings, particularly in obesity and in syndromes other than growth disorders have shown, that a series of factors have to be considered for a correct interpretation of the hormonal response to hypoglycemia. The limits for normal, reduced or absent response are given and as a simple screening for growth hormonee deficiency, a growth hormone estimation without stimulation can be used. The test has been found safe under clinical conditions and to provide reliable information about growth hormone and ACTH, respectively cortisol reaction.

The absence of intact growth hormone in urine as judged by radioimmunoassay

Non-specific factors in urine, measuring as apparent growth hormone, were detected when the radioimmunoassay for plasma growth hormone was applied to urine, dilute urine and fractions therefrom. Varying concentrations of salt and urea were shown to mimic the effect of growth hormone and, like the urine inhibition, were lost on dialysis. Urine from normal subjects and from a hypopituitary dwarf treated with growth hormone, when concentrated, desalted and fractionated by gel filtration gave no evidence for the presence of growth hormone. From recovery experiments it was concluded that growth hormone in normal urine is present at concentrations below 0·1 μg./I. An inhibitor with the immunological characteristics of growth hormone was obtained from a fraction of concentrated urine from an acromegalic patient and was equivalent to 0·24 μg. growth hormone/24 hr. urine.