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.

中文翻译：

---

生长激素替代可能影响甲状腺激素对肝脏和骨组织的生物学作用

客观的

生长激素 (GH) 替代改变了甲状腺素 (T4) 和三碘甲状腺原氨酸 (T3) 的外周相互转化。然而，关于这些改变的临床影响知之甚少。我们旨在将血清 T3:T4 比率中观察到的变化与来自不同外周组织的已知甲状腺激素作用生物标志物进行比较。

设计

我们在一家三级转诊内分泌中心前瞻性地研究了 20 名 GH 缺乏男性在 GH 替代之前和之后。血清生化测量包括胰岛素样生长因子-1 (IGF-1)、甲状腺激素（游离和总 T3、游离和总 T4 和反向 T3）和 TSH。将甲状腺激素浓度的变化与甲状腺激素作用的肝脏和骨骼生物标志物的变化进行了比较。

结果

GH 替代引起血清游离 T4 浓度下降（-1.09 ± 1.99 pmol/L；p = 0.02）和游离 T3 增加（+0.34 ± 0.15 pmol/L；p = 0.03）；因此，游离 T3：游离 T4 比率从 0.40 ± 0.02 增加到 0.47 ± 0.02 (p = 0.002)。性激素结合球蛋白（SHBG）水平没有变化。然而，血清铁蛋白的下降（-26.6 ± 8.5 ng/mL；p = 0.005）与 freeT4 的下降相关。脂质谱的改变，包括大 HDL 亚组分和 Lp (a) (+2.1 ± 21.1 nmol/L; p = 0.002) 的升高与甲状腺激素水平无关。血清骨转换标志物显着增加 - 前胶原 1 型氨基末端前肽 +57.4%；p = 0.0009，骨钙素 +48.6%；p = 0.0007；1 型胶原的 c-末端端肽 +73.7%；p = 0.002。

结论

GH 诱导的甲状腺轴改变与对甲状腺激素作用的复杂的组织特异性影响有关。骨转换标志物的调节表明 GH 可以改善甲状腺激素对骨骼的生物学作用。