Determination Of Insulin-like Growth factor-I Research Articles

High performance liquid chromatography — Ion trap mass spectrometry for the determination of insulin-like growth factor-I in house plasma

Insulin-like Growth Factor I is a marker of Somatotropin administration. In order to quantify this peptide in horse plasma samples, a high performance liquid chromatography/electrospray mass spectrometry method using R3 Insulin-like Growth Factor I as internal standard was developed. The extraction procedure involves an acid ethanol extraction and an immunoaffinity purification. Quantification is made possible by using deconvolution software and by measuring the insulin like growth factor-I/internal standard ratio. Comparison between high performance liquid chromatography/electrospray mass spectrometry and two immunological methods indicated agreement between methods even though more samples are needed to confirm this finding.

Insulin-like growth factor-I and its binding protein-3 in serum: are they good screening properties for the diagnosis of growth hormone deficiency?

Serum insulin-like growth factor-I and insulin-like growth factor binding protein-3 are simply-determined screening analytes if growth hormone deficiency is suspected. The analysis of growth hormone secretion using standardised stimulation tests and secretion profiles is complicated and expensive in comparison. In retrospect, we have examined the value of insulin-like growth factor-I and its binding protein-3 for the diagnostic clarification of patients with short stature (n = 117). In 39/117 patients growth hormone secretion was investigated as ward patients. Growth hormone deficiency was diagnosed in 10 patients, for 16 patients the diagnosis was neurosecretory dysfunction. For all patients (n = 7) with lowered insulin-like growth factor binding protein-3 and insulin-like growth factor-I values (insulin-like growth factor binding protein-3 < 5th percentile, insulin-like growth factor-I < 10th percentile) a growth hormone disorder was proven. Conversely, however, only 3/10 patients with classical growth hormone deficiency (n = 3) showed a lowering of both analytes. 8/10 patients with classical growth hormone deficiency and 8/16 patients with neurosecretory dysfunction had at least one lowered value. Two patients showed normal values for insulin-like growth factor-I and insulin-like growth factor binding protein-3 despite biochemically proven growth hormone deficiency. The combined determination of insulin-like growth factor-I and insulin-like growth factor binding protein-3 can provide valuable help during preliminary diagnosis of patients of short stature, indicating a disturbance of the growth hormone secretion if the values are lowered. Normal values do not, however, exclude the possibility of a growth hormone deficiency. Inpatient endocrinological testing is indispensible if growth hormone deficiency is suspected.

Preoperative octreotide treatment of growth hormone-secreting and clinically nonfunctioning pituitary macroadenomas: effect on tumor volume and lack of correlation with immunohistochemistry and somatostatin receptor scintigraphy.

The factors that determine the hormone and volume responses of pituitary adenomas to the somatostatin analog octreotide are poorly understood. We, therefore, studied the correlation between 111indium-pentetreotide somatostatin receptor scintigraphy (SRS) and the clinical and immunohistochemical classification of pituitary adenomas, on the one hand, and hormone and volume responses, on the other hand. Ten patients with GH-secreting (6 females and 4 males; age, 31-67 yr) and 14 patients with clinically nonfunctioning (NF) macroadenomas (5 females and 9 males; age, 22-79 yr) were preoperatively treated with 300 micrograms/day octreotide, which was increased to 600 and 1500 micrograms/day at weekly intervals and then continued for at least 3 months until surgery. SRS was performed before therapy. A sellar magnetic resonance imaging scan was performed before therapy; 1, 2, and 3 weeks and 3 months after start of therapy; and after surgery. Acromegalics also had an 8-h GH profile, insulin-like growth factor-I determination, and a 100-g oral glucose load at these time points. An attempt was made to identify NF adenomas as gonadotroph adenomas using their LH, FSH, and alpha-subunit responses to TRH. In acromegalic patients, octreotide suppressed mean GH (8-h profile) and insulin-like growth factor-I concentrations from 34.9 +/- 9.7 to 8.1 +/- 3.6 micrograms/L and from 2122 +/- 1025 to 701 +/- 208 micrograms/L, respectively, after 3 months. Significant (26-85% decline) tumor shrinkage occurred in 5 of 10 patients, mainly within the first week. Tumor shrinkage and GH suppression were not correlated. Four of 7 patients had increased pituitary 111indium-pentetreotide uptake, but this did not predict GH suppression or tumor shrinkage. Of the NF adenomas, 2 responded with shrinkage (57% and 96% decline). Four of 12 adenomas had increased 111indium-pentetreotide uptake, but this did not correlate with tumor shrinkage (2 adenomas; 1 gonadotroph and 1 null cell adenoma), immunohistochemistry, or clinical classification. We conclude that preoperative octreotide therapy suppresses GH in most patients and reduces tumor volume in up to 50% of acromegalic patients. It also induces shrinkage in some NF adenomas, although less frequently. SRS does not predict shrinkage of either tumor type. Shrinkage does not correlate with clinical classification or immunohistological characteristics. Further studies are needed to identify the factors that determine the hormone and volume responses of pituitary adenomas to octreotide therapy.

Determination of insulin-like growth factor-I in normal subjects and in patients with growth hormone disorders by radioimmunoassay using biosynthetic homologous peptide.

A highly sensitive and specific RIA for IGF-I has been developed using recombinant DNA-derived IGF-I of very high purity and specific antiserum to it. This assay system could detect IGF-I at as low concentrations as 20-30 ng/ml. The intra-assay and interassay coefficients of variation at various concentrations of IGF-I were 4.9 to 6.5% and 5.4 to 8.0%, respectively. The recovery rate of pure IGF-I added to plasma was 77.0 +/- 3.7%. The antiserum did not cross-react with porcine insulin, biosynthetic human insulin, hGH, hEGF, the synthetic C-domain of IGF-I or that of IGF-II, but reacted equally with an analog, Thr59-IGF-I. Plasma IGF-I was extracted by the acid-ethanol method before assay to separate IGF-I from its binding protein. When plasma IGF-I was assayed without extraction, the inhibition curves of serial dilution of plasma samples from several individuals were not parallel to the standard curve of IGF-I. The plasma concentration of IGF-I was 147 +/- 49 ng/ml (mean +/- SD) in 156 normal adults aged from 20-59 years. As reported by others, the IGF-I levels were low in cord plasma (41.8 +/- 23.5 ng/ml) and plasma of patients with GH deficiency (64.6 +/- 42.0 ng/ml), while its levels were high in normal children of pubertal ages (12-13 yr, 365 +/- 126 ng/ml) and in patients with active acromegaly (562 +/- 115 ng/ml). This RIA system is a simple and useful method for determining plasma IGF-I in normal and diseased states.