Ross D S
Department of Medicine, Massachusetts General Hospital, Boston 02144.
Am J Med. 1993 Oct;95(4):385-8. doi: 10.1016/0002-9343(93)90307-b.
Controversy exists as to whether patients with subclinical hypothyroidism benefit from treatment. Two randomized trials reported that hypothyroid symptoms improved following thyroid hormone replacement therapy. However, during the initial treatment of overt hypothyroidism with levothyroxine, three studies have demonstrated short-term (6 to 12 months) 5% to 13% reductions in bone density. The current study measures bone density during the initial treatment of subclinical hypothyroidism.
Seventeen postmenopausal women with subclinical hypothyroidism (elevated serum thyrotropin [TSH] and normal serum free thyroxine concentrations) and no prior history of thyroid disease were randomly assigned to levothyroxine treatment or no treatment and followed prospectively. Patients in the treatment group had similar initial serum TSH concentrations (9.8 +/- 3.3 versus 8.4 +/- 2.7 microU/mL) but were slightly older (68 +/- 7 years versus 60 +/- 5 years [p < 0.02]). The average dose of levothyroxine needed to normalize serum TSH concentration was 0.072 +/- 0.027 mg.
Bone density determinations were not significantly different between the two groups at baseline. After 14 +/- 1 months, single-photon absorptiometry of the wrist decreased by 1.8% +/- 3.2% in the untreated patients and 0.5% +/- 4.1% in the levothyroxine-treated patients (p = NS). Dual-energy X-ray absorptiometry of the lumbar spine decreased by 0.7% +/- 2.9% in the untreated patients and rose 0.1% +/- 4.75% in the levothyroxine-treated patients (p = NS).
Unlike the early treatment of overt hypothyroidism, there is no short-term reduction of bone density with levothyroxine treatment of subclinical hypothyroidism in postmenopausal women. These data suggest that potentially symptomatic women with subclinical hypothyroidism should be given a trial of levothyroxine therapy without concern about adverse effects on skeletal integrity.
亚临床甲状腺功能减退患者是否能从治疗中获益存在争议。两项随机试验报告称，甲状腺激素替代治疗后甲状腺功能减退症状有所改善。然而，在使用左甲状腺素初始治疗显性甲状腺功能减退期间，三项研究表明骨密度在短期内（6至12个月）降低了5%至13%。本研究测量亚临床甲状腺功能减退初始治疗期间的骨密度。
17名绝经后亚临床甲状腺功能减退女性（血清促甲状腺素[TSH]升高且血清游离甲状腺素浓度正常），既往无甲状腺疾病史，被随机分配接受左甲状腺素治疗或不治疗，并进行前瞻性随访。治疗组患者的初始血清TSH浓度相似（9.8±3.3对8.4±2.7微单位/毫升），但年龄稍大（68±7岁对60±5岁[p<0.02]）。使血清TSH浓度正常化所需的左甲状腺素平均剂量为0.072±0.027毫克。
两组在基线时骨密度测定无显著差异。14±1个月后，未治疗患者手腕的单光子吸收法测量值下降了1.8%±3.2%，左甲状腺素治疗患者下降了0.5%±4.1%（p=无统计学意义）。未治疗患者腰椎的双能X线吸收法测量值下降了0.7%±2.9%，左甲状腺素治疗患者上升了0.1%±4.75%（p=无统计学意义）。
与显性甲状腺功能减退的早期治疗不同，绝经后女性左甲状腺素治疗亚临床甲状腺功能减退不会导致短期内骨密度降低。这些数据表明，有潜在症状的亚临床甲状腺功能减退女性应尝试左甲状腺素治疗，而无需担心对骨骼完整性有不良影响。
