Dynamic changes of central thyroid functions in the management of Cushing's syndrome

ABSTRACT Objective The aim of this study was to determine the frequency of central thyroid dysfunctions in Cushing's syndrome (CS). We also aimed to evaluate the frequency of hyperthyroidism due to the syndrome of the inappropriate secretion of TSH (SITSH), which was recently defined in patients with insufficient hydrocortisone replacement after surgery. Materials and methods We evaluated thyroid functions (TSH and free thyroxine [fT4]) at the time of diagnosis, during the hypothalamo-pituitary-adrenal axis recovery, and after surgery in 35 patients with CS. The patients were separated into two groups: ACTH-dependent CS (group 1, n = 20) and ACTH-independent CS (group 2, n = 15). Patients’ clinical and laboratory findings were evaluated in five visits in the outpatient clinic of the endocrinology department. Results The frequency of baseline suppressed TSH levels and central hypothyroidism were determined to be 37% (n = 13) and 26% (n = 9), respectively. A negative correlation was found between baseline cortisol and TSH levels (r = -0.45, p = 0.006). All patients with central hypothyroidism and suppressed TSH levels showed recovery at the first visit without levothyroxine treatment. SITSH was not detected in any of the patients during the postoperative period. No correlation was found between prednisolone replacement after surgery and TSH or fT4 levels on each visit. Conclusion Suppressed TSH levels and central hypothyroidism may be detected in CS, independent of etiology. SITSH was not detected in the early postoperative period due to our adequate prednisolone replacement doses.

摘要
研究目的 本研究旨在明确库欣综合征（Cushing's syndrome, CS）患者中枢甲状腺功能异常的发生频率。此外，本研究还拟评估因术后氢化可的松替代治疗不足而新近定义的促甲状腺激素分泌不当综合征（syndrome of inappropriate secretion of TSH, SITSH）所致甲状腺功能亢进症的发生频率。
材料与方法 本研究纳入35例库欣综合征患者，分别于确诊时、下丘脑-垂体-肾上腺轴恢复期间以及术后评估其甲状腺功能（促甲状腺激素[thyroid-stimulating hormone, TSH]与游离甲状腺素[free thyroxine, fT4]）。将患者分为两组：促肾上腺皮质激素（adrenocorticotropic hormone, ACTH）依赖性库欣综合征（组1，n=20）与ACTH非依赖性库欣综合征（组2，n=15）。于内分泌科门诊的5次随访中评估患者的临床与实验室检查结果。
结果 基线TSH水平受抑以及中枢性甲状腺功能减退症的发生频率分别为37%（n=13）与26%（n=9）。基线皮质醇水平与TSH水平呈负相关（r=-0.45，P=0.006）。所有合并中枢性甲状腺功能减退症及TSH水平受抑的患者均在首次随访时无需左甲状腺素（levothyroxine）治疗即可恢复。术后随访期间未检测出任何1例SITSH患者。术后泼尼松龙替代治疗剂量与各随访时点的TSH或fT4水平均无相关性。
结论 库欣综合征患者可出现TSH水平受抑与中枢性甲状腺功能减退症，且该表现与病因无关。本研究中因术后采用了足量的泼尼松龙替代治疗，故早期术后阶段未检测出SITSH。