Tanis B C, Westendorp G J, Smelt H M
Department of Clinical Epidemiology, Leiden University Hospital, The Netherlands.
Clin Endocrinol (Oxf). 1996 Jun;44(6):643-9. doi: 10.1046/j.1365-2265.1996.739560.x.
The significance of mild hypercholesterolaemia in subclinical hypothyroidism and whether there is beneficial reduction after thyroxine replacement, remain controversial. We aimed to describe the association between hypercholesterolaemia and subclinical hypothyroidism, and to quantify the effect of thyroid substitution therapy by an analysis of previously published intervention studies.
Intervention studies cited in the Medline database from January 1976 until January 1995, with index terms cholesterol, hypercholesterolaemia, hyperlipidaemia, thyrotrophin (TSH), hypothyroidism, thyroid and human. A total of 148 studies were reviewed.
We recorded the year of publication, study design, number of patients enrolled, mean age, duration of thyroid substitution, normal range of TSH levels, TSH levels pre and post-substitution treatment and total cholesterol in plasma before and after treatment.
(1) Qualitative description of studies on the relationship between hypercholesterolaemia and hypothyroidism, both subclinical and clinical. (2) Precision weighted pooled estimates of the effect of thyroid substitution therapy on the plasma levels of total cholesterol, in patients with subclinical and overt hypothyroidism.
Subclinical hypothyroidism was two to three times more frequent in people with an elevated total plasma cholesterol. In addition, the total plasma cholesterol levels were slightly elevated in patients with subclinical dysfunction of the thyroid. Thyroid substitution therapy in patients with subclinical hypothyroidism, restoring the TSH levels to normal, decreased total cholesterol by 0.4 mmol/l (95% confidence interval (Cl) 0.2-0.6 mmol/l) independently of the initial plasma level. The effect of thyroid substitution therapy on HDL-cholesterol in patients with subclinical hypothyroidism was not consistent. The effect of thyroid substitution in patients with overt hypothyroidism was highly dependent on the pretreatment levels of total cholesterol. In these patients substitution therapy decreased total cholesterol by 1.2 mmol/l (95% Cl 0.9-1.5 mmol/l) when the plasma levels were elevated up to 8 mmol/l, and by 3.4 mmol/l (95% Cl 3.0-3.7) when plasma levels were higher than 8 mmol/l. The high density lipoprotein (HDL)-cholesterol level decreased and amounted to 0.16 mmol/l (95% Cl 0.07-0.24).
Thyroid substitution treatment in patients with hypercholesterolaemia and subclinical hypothyroidism decreases total plasma cholesterol by 0.4 mmol/l, but plasma levels remain elevated in most patients. Further treatment with dietary restriction and cholesterol synthesis inhibitors should then be considered.
轻度高胆固醇血症在亚临床甲状腺功能减退中的意义以及甲状腺素替代治疗后胆固醇是否会有益降低仍存在争议。我们旨在描述高胆固醇血症与亚临床甲状腺功能减退之间的关联，并通过对先前发表的干预性研究进行分析来量化甲状腺替代治疗的效果。
1976年1月至1995年1月Medline数据库中引用的干预性研究，索引词为胆固醇、高胆固醇血症、高脂血症、促甲状腺激素（TSH）、甲状腺功能减退、甲状腺和人类。共审查了148项研究。
我们记录了发表年份、研究设计、纳入患者数量、平均年龄、甲状腺替代治疗持续时间、TSH水平正常范围、替代治疗前后的TSH水平以及治疗前后血浆总胆固醇水平。
（1）对高胆固醇血症与亚临床和临床甲状腺功能减退之间关系的研究进行定性描述。（2）对亚临床和显性甲状腺功能减退患者中甲状腺替代治疗对血浆总胆固醇水平影响的精确加权合并估计。
血浆总胆固醇升高的人群中亚临床甲状腺功能减退的发生率高出两到三倍。此外，亚临床甲状腺功能障碍患者的血浆总胆固醇水平略有升高。亚临床甲状腺功能减退患者进行甲状腺替代治疗，使TSH水平恢复正常，可使总胆固醇降低0.4 mmol/l（95%置信区间（Cl）0.2 - 0.6 mmol/l），与初始血浆水平无关。甲状腺替代治疗对亚临床甲状腺功能减退患者高密度脂蛋白胆固醇（HDL - 胆固醇）的影响并不一致。显性甲状腺功能减退患者的甲状腺替代治疗效果高度依赖于治疗前的总胆固醇水平。在这些患者中，当血浆水平升高至8 mmol/l时，替代治疗使总胆固醇降低1.2 mmol/l（95% Cl 0.9 - 1.5 mmol/l），当血浆水平高于8 mmol/l时，降低3.4 mmol/l（95% Cl 3.0 - 3.7）。高密度脂蛋白（HDL）胆固醇水平降低至0.16 mmol/l（95% Cl 0.07 - 0.24）。
高胆固醇血症合并亚临床甲状腺功能减退患者进行甲状腺替代治疗可使血浆总胆固醇降低0.4 mmol/l，但大多数患者的血浆水平仍升高。随后应考虑采用饮食限制和胆固醇合成抑制剂进行进一步治疗。
