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Circadian variation in serum free and total insulin-like growth factor (IGF)-I and IGF-II in untreated and treated acromegaly and growth hormone deficiency.

Abstract：

OBJECTIVE:It is generally accepted that there is no clinically significant circadian variation in total insulin-like growth factor (IGF)-I or total IGF-II in healthy subjects. In contrast there is a significant nocturnal decrease in free IGF-I in healthy subjects, corresponding to the nocturnal increase in IGF binding protein-1. In this study we have investigated the circadian variation in circulating free IGF-I and IGF-II in patients with acromegaly and patients with adult onset growth hormone deficiency. PATIENTS:Seven acromegalic patients were studied with and without treatment with a slow-release formulation of octreotide. Seven GH-deficient patients were studied without GH replacement. In addition 5 of the GH-deficient patients were studied during GH replacement. DESIGN:Serum samples were obtained every hour for 24 h. Free IGF-I and IGF-II were measured every 2nd hour. Total IGF-I and IGF-II were measured every 2nd hour (acromegalic patients) or every 4th hour (GH deficient patients). IGF binding protein (IGFBP)-1 was measured every 2nd hour (acromegalic patients) or every hour (GH deficient patients). RESULTS:In the untreated acromegalic patients there was a significant nocturnal decrease in free IGF-I, but not free IGF-II, before treatment. During treatment there was a significant nocturnal decrease in both free IGF-I and free IGF-II. Peak values of free IGF-I were 112% and 75% above trough (treatment and withdrawal, respectively). In the GH-deficient patients there were no significant circadian variations in free IGF-I or free IGF-II in either of the two occasions. In contrast, there was a significant circadian variation of total IGF-I after adjustment for changes in plasma volume in both treated and untreated acromegaly and GH deficiency in all cases with a peak between 0300 h and 0400 h. The nocturnal increase in total IGF-I ranged from 20% to 35%. CONCLUSIONS:A significant circadian variation in free IGF-I and IGF-II was demonstrated in acromegalic patients. In contrast no significant circadian variation in free IGF-I and IGF-II was found in GH-deficient patients. Part of the variations may be due to poorly understood variations in IGF-I release. It is not clear whether and to what extent the observed circadian changes in free and total IGF-I are involved in circadian changes in IGF-I bioactivity.

journal_name

Clin Endocrinol (Oxf)

journal_title

Clinical endocrinology

authors

Skjaerbaek C,Frystyk J,Kaal A,Laursen T,Møller J,Weeke J,Jørgensen JO,Sandahl Christiansen J,Orskov H

doi

10.1046/j.1365-2265.2000.00876.x

keywords:

subject

Has Abstract

pub_date

2000-01-01 00:00:00

pages

25-33

issue

eissn

0300-0664

issn

1365-2265

pii

cen876

journal_volume

pub_type

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Circadian variation in serum free and total insulin-like growth factor (IGF)-I and IGF-II in untreated and treated acromegaly and growth hormone deficiency.