Effect of insulin-like growth factor I on the thyroid axis in patients with Laron-type dwarfism and healthy subjects.
We have evaluated the effect of exogenous administration of IGF-I on the thyroid axis in four separate studies: (1) iv bolus injection; (2) single sc injection; (3) seven days' sc treatment, and (4) four months' treatment. Thirteen patients with Laron-type dwarfism (LTD) participated in the investigations. In studies 1 and 2, 10 healthy subjects were also included. Before and during long-term treatment (study 4) six LTD patients underwent a TRH test. IGF-I was administered in a dose of 75 micrograms.kg-1 iv or 120-150 micrograms.kg-1 sc. Single injections of IGF-I caused significant decreases of serum TSH in LTD patients (iv: 1.7 +/- 0.2 to 1.1 +/- 0.1 mU/l; sc: from 2.1 +/- 0.4 to 1.1 +/- 0.2; p < 0.0005). In controls the decrease was for iv from 1.2 +/- 0.2 to 0.8 +/- 0.2 mU/l (p < 0.02) and for sc from 2.0 +/- 0.5 to 0.8 +/- 0.2 mU/l (p < 0.05). Long-term administration of IGF-I induces a transitory decrease of both serum TSH and fT4, followed by a spontaneous rise to pretreatment or even higher values. No changes in T3 were observed. TSH stimulation by TRH was significantly augmented after four months of IGF-I treatment (p < 0.005). The effects of IGF-I can be explained by an early stimulation of somatostatin release causing a decrease in TSH and followed by the development of compensatory mechanisms. All changes were within the normal ranges, not causing abnormal thyroid function.(ABSTRACT TRUNCATED AT 250 WORDS)
Institute of Pediatric and Adolescent Endocrinology, Children's Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Israel.
B
B
Klinger
A
A
Ionesco
S
S
Anin
Z
Z
Laron
D000293:Adolescent; D000328:Adult; D002648:Child; D004392:Dwarfism / Q000097:blood / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D011994:Recombinant Proteins / Q000494:pharmacology; D013004:Somatostatin / Q000378:metabolism / Q000502:physiology; D013961:Thyroid Gland / Q000378:metabolism / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
D011994:Recombinant Proteins; D014284:Triiodothyronine; D013004:Somatostatin; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013974:Thyroxine