原发性甲状腺功能减退症致垂体增生的诊断难点与误诊分析

Hard nut to crack in diagnosis of pituitary hyperplasia secondary to primary hypothyroidism and reasons of misdiagnosis

目的根据原发性甲状腺功能减退症致垂体增生的临床及磁共振（MRI）表现，探讨疑难病例诊断原则和误诊原因。方法对10例确诊甲状腺功能减退症致垂体增生患者治疗前后的临床资料和MRI进行回顾性分析。结果10例实验室检查结果符合原发性甲状腺功能减退症的患者，垂体MRI平扫均可见对称性增大，信号均匀，增强后垂体均匀强化。经甲状腺素替代治疗3—6个月后MRI示垂体恢复正常7例，垂体明显缩小2例；血浆甲状腺素、促甲状腺素（TSH）和催乳素（PRL）水平恢复正常9例。另1例因误诊为垂体腺瘤行γ-刀治疗，致永久性甲状腺功能减退。结论原发性甲状腺功能减退症致垂体增生的临床及MRI表现具有一定特点，但确诊需密切结合实验室检查。提高对垂体增生的认识，可避免不必要的垂体干预治疗。

Objective To analyze the difficulty in diagnosis of pituitary hyperplasia secondary to primary hypothyroidism and reasons of misdiagnosis. Methods Ten patients with clinical manifestations of primary hypothyroidism, 3 males and 7 females, aged 7 - 26, underwent MR imaging and serum hormone examination before and after thyroid hormone replacement therapy. Tl-weighted images without and with contrast material enhancement in sagittal and coronal planes were obtained. Serum free triiodothyronine, free thyroxine, thyrotropic-stimnlating hormone and prolactin （PRL） levels were measured. Results Obvious symmetrical enlargement of the pituitary gland with homogeneous signal intensity was revealed by MRI in all the patients. The height of the pituitary ranged 1.2 - 2.2 cm. The pituitary glands appeared homogeneously enhanced after Gd-DTPA administration. After 3 - 6 months of L-thyroxin replacement therapy, follow-up MRI showed that the pituitary glands reduced in size markedly in 9 cases, and the plasma thyroxine, TSH, and PRL levels of these 9 cases turned normal. One patient was misdiagnosed as with maeroadenoma and was treated with gamma knife, resulting in permanence hypothyroidism. Conclusion Symmetrical enlargement of pituitary gland with homogeneously enhancement on MRI has great diagnostic value in pituitary hyperplasia with primary hypothyroidism. Thyroid hormone replacement therapy can cause regression of the enlarged pituitary, thus avoiding unnecessary surgery.