Insulin-like growth factor binding protein-3 (IGFBP-3) is the major carrier of insulin-like growth factor I (IGF-1) in serum, and its production is growth hormone (GH) dependent. It is unclear whether in humans IGFBP-3 production is directly regulated by GH or mediated via IGF-I. We addressed this question in six patients with Laron-type dwarfism, a syndrome characterized by the absence of GH receptor activity (LTD), who were chronically treated with recombinant IGF-I. Analysis of the electrophoretic profiles of serum IGFBPs in these patients by Western ligand blotting revealed an extremely low IGFBP-3 level. A striking progressive increase in serum IGFBP-3 was observed with continuous treatment, despite the absence of GH action. In LTD children, serum IGFBP-3 increased up to 19-fold after six months of therapy and equalled levels observed in controls, whereas in adult LTD patients the increase was smaller. A rise in serum levels of 34, 30 and 24 kDa BPs (presumably IGFBP-2, -1 and -4, respectively was also noted with chronic IGF-I therapy. This proof of GH-independent induction of IGFBP-3 by IGF-1 may be a major advantage in the therapeutic use of biosynthetic IGF-I in several types of short stature children.
Hannah Kanety, Avraham Karasik, Beatrice Klinger, Aviva Silbergeld and Zvi Laron
Ohad Cohen, Jacob Ilany, Chen Hoffman, David Olchovsky, Sari Dabhi, Avraham Karasik, Elinor Goshen, Galina Rotenberg and S Tzila Zwas
Objective: We aimed to assess low-dose recombinant human thyroid-stimulating hormone (rhTSH)-aided, fixed-activity radioiodine therapy of large, multinodular goiters (MNGs) in elderly patients with comorbidities.
Design: This was a short-term, observational study.
Methods: We measured 24-h thyroid radioiodine uptake (RAIU) of 2 μCi 131-iodine at baseline and 24 h after intramuscular injection of 0.03 mg rhTSH in 17 patients (aged 60–86 years, 12 women), who subsequently received 30 mCi 131-iodine 24 h after an identical rhTSH injection. TSH and free thyroxine (FT4) were measured at baseline and days 10, 30 and 90 after therapy. Thyroid volume was assessed by computed tomography at baseline and day 180.
Results: rhTSH, 0.03 mg, significantly increased mean 24-h thyroid RAIU from 25.8% ± 10.3% to 43.3% ± 8.4% (68% relative increase; t(16) = −8.43, P < 0.001). The proportion of patients overtly or subclinically hyperthyroid (TSH < 0.5 mU/l) decreased from 71% (12/17) at baseline to 19% (3/16) at 3 months. Mean serum FT4 peaked at slightly above normal range, 25.9 ± 7.7 pmol/l (46% over baseline) and was 21% under baseline levels at 3 months. Mean estimated thyroid volume fell 34% from baseline to 6 months (170.0 ± 112.8 to 113.1 ± 97.5 ml; P < 0.01). Symptomatic relief, improved well-being, and/or reduction or elimination of antihyperthyroid medication were seen in 76% of patients. Three (18%) patients had transient neck pain or tenderness, or palpitations; one had transient asymptomatic thyroid enlargement; and three (18%) became hypothyroid by 3 months.
Conclusions: Intramuscular rhTSH, 0.03 mg, followed 24 h later by 30 mCi 131-iodine, is a safe, effective and convenient treatment for MNG in elderly patients with comorbidities.