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)
Klinger
B
B
Institute of Pediatric and Adolescent Endocrinology, Children's Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Israel.
Ionesco
A
A
Anin
S
S
Laron
Z
Z
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