Nigel Glynn , David J. Halsall , Gerard Boran , Paul Cook , John H. McDermott , Diarmuid Smith , William Tormey , Christopher J. Thompson , Donal O'Gorman , Malachi J. McKenna , Amar Agha
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引用次数: 6
Abstract
Objective
Growth hormone (GH) replacement alters the peripheral interconversion of thyroxine (T4) and triiodothyronine (T3). However, little is known about the clinical impact of these alterations. We aimed to compare changes observed in the serum T3:T4 ratio with known biological markers of thyroid hormone action derived from different peripheral tissues.
Design
We prospectively studied twenty GH deficient men before and after GH replacement in a tertiary referral endocrine center. Serum biochemical measurements included insulin like growth factor-1 (IGF-1), thyroid hormones (free & total T3, free & total T4 and reverse T3) and TSH. Changes in thyroid hormone concentration were compared to alterations in hepatic and bone biomarkers of thyroid hormone action.
Results
GH replacement provoked a decline in serum free T4 concentration (−1.09 ± 1.99 pmol/L; p = 0.02) and an increase in free T3 (+0.34 ± 0.15 pmol/L; p = 0.03); therefore, the free T3:free T4 ratio increased from 0.40 ± 0.02 to 0.47 ± 0.02 (p = 0.002). Sex hormone binding globulin (SHBG) level was unchanged. However, a decline in serum ferritin (−26.6 ± 8.5 ng/mL; p = 0.005) correlated with a fall in freeT4. Alterations in lipid profile, including a rise in large HDL sub-fractions and Lp (a) (+2.1 ± 21.1 nmol/L; p = 0.002) did not correlate with thyroid hormone levels. Significant increases were recorded in serum bone turnover markers - procollagen type 1 amino-terminal propeptide +57.4%; p = 0.0009, osteocalcin +48.6%; p = 0.0007; c-terminal telopeptides of type 1 collagen +73.7%; p = 0.002. Changes in bone formation markers occurred in parallel with fluctuations in thyroid hormone.
Conclusion
GH-induced alterations in the thyroid axis are associated with complex, tissue specific effects on thyroid hormone action. Modulation of bone turnover markers suggests that GH may improve the biological action of thyroid hormone on bone.
期刊介绍：
Growth Hormone & IGF Research is a forum for research on the regulation of growth and metabolism in humans, animals, tissues and cells. It publishes articles on all aspects of growth-promoting and growth-inhibiting hormones and factors, with particular emphasis on insulin-like growth factors (IGFs) and growth hormone. This reflects the increasing importance of growth hormone and IGFs in clinical medicine and in the treatment of diseases.
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