Bhadada S K, Cardenas M, Bhansali A, Mittal B R, Behera A, Chanukya G V, Nahar U, Rao D Sudhaker
Department of Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Clin Endocrinol (Oxf). 2008 Sep;69(3):382-5. doi: 10.1111/j.1365-2265.2008.03225.x. Epub 2008 Feb 18.
To report and explore potential reasons for undetectable or low-normal serum intact PTH levels in patients with surgically verified primary hyperparathyroidism with parathyroid adenomas, review the relevant literature, and offer suggestions for management of such patients occasionally encountered in clinical practice. For future research, to help understand mechanisms underlying 'undetectable' or inappropriately low serum intact PTH levels.
Serum intact PTH levels were measured pre- and postoperatively by immunochemiluminescent assay (ICMA) and the results were confirmed by at least two repeated measurements on different occasions in each patient.
We encountered two unusual patients with primary hyperparathyroidism who had suggestive biochemical and/or clinical features of primary hyperparathyroidism. However, serum intact PTH levels were either very low or undetectable in the context of hypercalcaemia, with no other obvious cause. A (99m)Tc sestamibi scan showed increased uptake in one of the parathyroid glands, suggesting a single adenoma in each case that was confirmed at surgery.
In the first patient, from India, mean +/- SD serum calcium was 2.6 +/- 0.32 mmol/l (reference range 2.12-2.74 mmol/l) with intact PTH of 0.11 pmol/l (reference range 1.1-7.59 pmol/l). In the second patient, from the USA, mean +/- SD serum calcium and intact PTH were 2.9 +/- 0.07 mmol/l (reference range 2.17-2.51 mmol/l) and 1.35 pmol/l (reference range 1.1-7.59 pmol/l), respectively. Following curative parathyroidectomy, serum calcium levels normalized in both patients. By contrast, serum intact PTH levels, which were either suppressed or very low before surgery, rose into the low-normal reference range in all patients.
When the clinical suspicion is high, the diagnosis of primary hyperparathyroidism should be pursued despite suppressed or low-normal serum intact PTH levels after carefully excluding other causes of hypercalcaemia. Further research on various intact PTH molecular species secreted by parathyroid adenomas or post-translational changes in the intact PTH molecule that might interfere with in vitro measurements should be undertaken to understand the precise reason(s) for such anomalous findings.
报告并探讨经手术证实患有甲状旁腺腺瘤的原发性甲状旁腺功能亢进患者血清完整甲状旁腺激素（PTH）水平检测不到或处于低正常范围的潜在原因，回顾相关文献，并为临床实践中偶尔遇到的此类患者的管理提供建议。为未来的研究提供帮助，以了解“检测不到”或血清完整PTH水平异常降低的潜在机制。
通过免疫化学发光分析法（ICMA）在术前和术后测量血清完整PTH水平，每位患者在不同时间至少重复测量两次以确认结果。
我们遇到了两名不寻常的原发性甲状旁腺功能亢进患者，他们具有原发性甲状旁腺功能亢进的生化和/或临床特征。然而，在高钙血症的情况下，血清完整PTH水平非常低或检测不到，且无其他明显原因。（99m）锝甲氧基异丁基异腈扫描显示其中一个甲状旁腺摄取增加，提示每例均为单个腺瘤，手术证实了这一点。
第一名患者来自印度，血清钙均值±标准差为2.6±0.32 mmol/L（参考范围2.12 - 2.74 mmol/L），完整PTH为0.11 pmol/L（参考范围1.1 - 7.59 pmol/L）。第二名患者来自美国，血清钙均值±标准差和完整PTH分别为2.9±0.07 mmol/L（参考范围2.17 - 2.51 mmol/L）和1.35 pmol/L（参考范围1.1 - 7. pmol/L）。在进行根治性甲状旁腺切除术后，两名患者的血清钙水平均恢复正常。相比之下，术前被抑制或非常低的血清完整PTH水平在所有患者中均升至低正常参考范围。
当临床怀疑度较高时，在仔细排除高钙血症的其他原因后，尽管血清完整PTH水平被抑制或处于低正常范围，仍应进行原发性甲状旁腺功能亢进的诊断。应进一步研究甲状旁腺腺瘤分泌的各种完整PTH分子种类或完整PTH分子的翻译后变化，这些变化可能会干扰体外测量，以了解此类异常结果的确切原因。
