Drobny E C, Amburn K, Baumann G
J Clin Endocrinol Metab. 1983 Sep;57(3):524-8. doi: 10.1210/jcem-57-3-524.
Human GH (hGH) circulating during periods of basal pituitary secretion is frequently undetectable in human plasma by RIA. Such basal periods predominate throughout most of the day. Knowledge of the concentration of basal hGH is important, since hGH plays a role in the homeostasis of several metabolic fuels and ions. We have used an immunoadsorbent technique to extract and concentrate hGH from large plasma samples before RIA in order to precisely measure basal hGH levels [immunoextracted RIA (IERIA)]. Twenty milliliters of blood were drawn from five normal volunteers every 2 h over a 24-h period. The obtained plasma (10-13 ml) was passed over an anti-hGH antibody Sepharose column. The column-bound hGH was eluted and measured by RIA. Recovery of hGH in the plasma extracts was measured using [131I]hGH as an internal standard. Recovery averaged 54 +/- 12% (mean +/- SD). Theoretically, the extraction procedure expanded the useful range of the RIA about 50-fold. In practice, the detection limit was 40 pg/ml plasma. Basal hGH (defined as less than 1 ng/ml by conventional RIA) was found to range from less than 40 to 746 pg/ml by IERIA. Above 2 ng/ml, conventional RIA and IERIA yielded comparable results (r = 0.92; P less than 0.001), but below 2 ng/ml, the two assays did not correlate (r = 0.01; P greater than 0.5). In general, conventional RIA overestimated plasma hGH in that range. As a result, the ratio between nocturnal and daytime hGH secretion, as assessed by IERIA, is higher than previously appreciated. We conclude that basal plasma hGH is highly variable below 1 ng/ml, and may on occasion be as low as less than 40 pg/ml. The episodic nature of hGH release appears to persist in the basal state. The conventional definition for basal hGH (less than 5 ng/ml) should probably be revised downward to less than 0.8 ng/ml.
在垂体基础分泌期循环的人生长激素（hGH），通过放射免疫分析法（RIA）在人血浆中常常检测不到。这种基础分泌期在一天中的大部分时间占主导。了解基础hGH的浓度很重要，因为hGH在几种代谢燃料和离子的体内平衡中起作用。我们使用免疫吸附技术在RIA检测前从大量血浆样本中提取和浓缩hGH，以便精确测量基础hGH水平[免疫提取RIA（IERIA）]。在24小时内，每2小时从五名正常志愿者身上抽取20毫升血液。将获得的血浆（10 - 13毫升）通过抗hGH抗体琼脂糖柱。将柱结合的hGH洗脱并用RIA测量。使用[131I]hGH作为内标测量血浆提取物中hGH的回收率。回收率平均为54±12％（平均值±标准差）。从理论上讲，提取程序将RIA的有效范围扩大了约50倍。实际上，检测限为40 pg/ml血浆。通过IERIA发现基础hGH（通过传统RIA定义为小于1 ng/ml）范围为小于40至746 pg/ml。高于2 ng/ml时，传统RIA和IERIA产生可比结果（r = 0.92；P小于0.001），但低于2 ng/ml时，两种测定不相关（r = 0.01；P大于0.5）。一般来说，传统RIA在该范围内高估了血浆hGH。结果，通过IERIA评估的夜间和白天hGH分泌之间的比率高于先前的认识。我们得出结论，基础血浆hGH在低于1 ng/ml时高度可变，并且有时可能低至小于40 pg/ml。hGH释放的脉冲性质在基础状态下似乎持续存在。基础hGH的传统定义（小于5 ng/ml）可能应向下修订为小于0.8 ng/ml。
