Central hypothyroidism is a rare and heterogeneous disorder that is characterized by a defect in thyroid hormone secretion in an otherwise normal thyroid gland due to insufficient stimulation by TSH. The disease results from the abnormal function of the pituitary gland, the hypothalamus, or both. Moreover, central hypothyroidism can be isolated or combined with other pituitary hormone deficiencies, which are mostly acquired and are rarely congenital. The clinical manifestations of central hypothyroidism are usually milder than those observed in primary hypothyroidism. Obtaining a positive diagnosis for central hypothyroidism can be difficult from both a clinical and a biochemical perspective. The diagnosis of central hypothyroidism is based on low circulating levels of free T₄ in the presence of low to normal TSH concentrations. The correct diagnosis of both acquired (also termed sporadic) and congenital (also termed genetic) central hypothyroidism can be hindered by methodological interference in free T₄ or TSH measurements; routine utilization of total T₄ or T₃ measurements; concurrent systemic illness that is characterized by low levels of free T₄ and normal TSH concentrations; the use of the sole TSH-reflex strategy, which is the measurement of the sole level of TSH, without free T₄, if levels of TSH are in the normal range; and the diagnosis of congenital hypothyroidism based on TSH analysis without the concomitant measurement of serum levels of T₄. In this Review, we discuss current knowledge of the causes of central hypothyroidism, emphasizing possible pitfalls in the diagnosis and treatment of this disorder.

中文翻译：

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中枢性甲状腺功能减退症-一种被忽略的甲状腺疾病

中枢性甲状腺功能减退症是一种罕见的异质性疾病，其特征是由于TSH刺激不足而导致正常甲状腺中甲状腺激素分泌缺陷。该疾病是由垂体，下丘脑或两者的异常功能引起的。此外，中枢性甲状腺功能减退症可以被隔离或与其他垂体激素缺乏症合并使用，这些大多是后天性的，很少是先天性的。中枢性甲状腺功能减退症的临床表现通常比原发性甲状腺功能减退症轻。从临床和生化的角度来看，都很难获得中央性甲状腺功能减退的阳性诊断。中枢性甲状腺功能减退症的诊断基于游离T _4的低循环水平在低至正常TSH浓度的情况下。通过对自由T ₄或TSH测量的方法学干预，可能会妨碍对获得性（也称为散发性）和先天性（也称为遗传性）中央甲状腺功能减退症的正确诊断。常规使用总的T ₄或T ₃测量值；并发全身性疾病，其特征在于游离T ₄含量低和正常TSH浓度；如果TSH水平在正常范围内，则使用唯一的TSH反射策略，该策略是在没有游离T _4的情况下测量TSH的唯一水平；TSH分析的先天性甲状腺功能减退症的诊断和诊断，而无需同时测定血清T ₄水平。在这篇综述中，我们讨论了有关中枢性甲状腺功能低下的原因的当前知识，强调了该疾病的诊断和治疗中可能存在的陷阱。