Boston University School of Medicine, Boston Medical Center, Boston, MA, USA.
University of Pittsburgh Medical Center St. Margaret Family Medicine Residency Program, Pittsburgh, PA, USA.
Am Fam Physician. 2021 May 15;103(10):605-613.
Clinical hypothyroidism affects one in 300 people in the United States, with a higher prevalence among female and older patients. Symptoms range from minimal to life-threatening (myxedema coma); more common symptoms include cold intolerance, fatigue, weight gain, dry skin, constipation, and voice changes. The signs and symptoms that suggest thyroid dysfunction are nonspecific and nondiagnostic, especially early in disease presentation; therefore, a diagnosis is based on blood levels of thyroid-stimulating hormone and free thyroxine. There is no evidence that population screening is beneficial. Symptom relief and normalized thyroid-stimulating hormone levels are achieved with levothyroxine replacement therapy, started at 1.5 to 1.8 mcg per kg per day. Adding triiodothyronine is not recommended, even in patients with persistent symptoms and normal levels of thyroid-stimulating hormone. Patients older than 60 years or with known or suspected ischemic heart disease should start at a lower dosage of levothyroxine (12.5 to 50 mcg per day). Women with hypothyroidism who become pregnant should increase their weekly dosage by 30% up to nine doses per week (i.e., take one extra dose twice per week), followed by monthly evaluation and management. Patients with persistent symptoms after adequate levothyroxine dosing should be reassessed for other causes or the need for referral. Early recognition of myxedema coma and appropriate treatment is essential. Most patients with subclinical hypothyroidism do not benefit from treatment unless the thyroid-stimulating hormone level is greater than 10 mIU per L or the thyroid peroxidase antibody is elevated.
美国每 300 人中就有 1 人患有临床甲状腺功能减退症，女性和老年患者的患病率更高。症状从轻微到危及生命（黏液性水肿昏迷）；更常见的症状包括怕冷、疲劳、体重增加、皮肤干燥、便秘和声音变化。提示甲状腺功能障碍的体征和症状是非特异性和非诊断性的，尤其是在疾病早期；因此，诊断基于促甲状腺激素和游离甲状腺素的血液水平。没有证据表明人群筛查有益。通过左甲状腺素替代治疗可缓解症状并使促甲状腺激素水平正常化，起始剂量为每天每公斤 1.5 至 1.8 微克。不建议添加三碘甲状腺原氨酸，即使在持续存在症状和促甲状腺激素水平正常的患者中也是如此。年龄大于 60 岁或有已知或疑似缺血性心脏病的患者应从较低的左甲状腺素剂量（每天 12.5 至 50 微克）开始。患有甲状腺功能减退症的女性在怀孕后应将每周剂量增加 30%，最多每周 9 剂（即每周两次额外服用一剂），然后每月进行评估和管理。在充分给予左甲状腺素剂量后仍有持续症状的患者应重新评估其他原因或是否需要转诊。早期识别黏液性水肿昏迷并进行适当治疗至关重要。大多数亚临床甲状腺功能减退症患者不会从治疗中获益，除非促甲状腺激素水平大于 10 mIU/L 或甲状腺过氧化物酶抗体升高。
