Elevated IGF-1 with GH suppression after an oral glucose overload: incipient acromegaly or false-positive IGF-1?

ABSTRACT Objective To report the evolution of patients with a suggestive clinical scenario and elevated serum insulin-like growth factor-1 (IGF-1), but growth hormone (GH) suppression in the oral glucose tolerance test (OGTT), in whom acromegaly was not initially excluded. Subjects and methods Forty six patients with a suggestive clinical scenario, who had elevated IGF-1 (outside puberty and pregnancy) in two measurements, but GH < 0.4 µg/L in the OGTT, were selected. Five years after initial evaluation, the patients were submitted to clinical and laboratory (serum IGF-1) reassessment. Patients with persistently elevated IGF-1 were submitted to a new GH suppression test and magnetic resonance imaging (MRI) of the pituitary. Results Four patients were lost to follow-up. During reassessment, 42 patients continued to show no “typical phenotype” or changes in physiognomy. Fifteen of the 42 patients had normal IGF-1. Among the 27 patients with persistently elevated IGF-1 and who were submitted to a new OGTT, GH suppression was confirmed in all. Two patients exhibited a lesion suggestive of microadenoma on pituitary MRI. In our interpretation of the results, acromegaly was ruled out in 40 patients and considered “possible” in only 2. Conclusion Our results show that even in patients with a suggestive clinical scenario and elevated IGF-1, confirmed in a second measurement and without apparent cause, acromegaly is very unlikely in the case of GH suppression in the OGTT.

摘要 目的 报告存在疑似临床表型、血清胰岛素样生长因子-1（insulin-like growth factor-1, IGF-1）升高，但口服葡萄糖耐量试验（oral glucose tolerance test, OGTT）中生长激素（growth hormone, GH）受抑制，且最初未排除肢端肥大症的患者的病情演变情况。对象与方法 选取46例符合以下条件的患者：存在疑似临床表型，两次检测均发现IGF-1升高（排除青春期及妊娠状态），但口服葡萄糖耐量试验中生长激素水平＜0.4 µg/L。于初次评估5年后，对所有患者进行临床及实验室（血清IGF-1）复查。对于持续存在IGF-1升高的患者，再次行生长激素抑制试验及垂体磁共振成像（magnetic resonance imaging, MRI）检查。结果 4例患者失访。复查期间，42例患者未出现"典型表型"或面容改变。42例患者中15例IGF-1恢复正常。在27例持续IGF-1升高且接受再次口服葡萄糖耐量试验的患者中，所有受试者均证实存在生长激素抑制。2例患者的垂体磁共振成像可见疑似微腺瘤的病灶。经研判，40例患者可排除肢端肥大症，仅2例考虑为"疑似"病例。结论 本研究结果显示，即便患者存在疑似临床表型、两次检测均证实IGF-1升高且无明确诱因，若口服葡萄糖耐量试验中存在生长激素抑制，其罹患肢端肥大症的可能性极低。