Kabadi U M
Veterans Affairs Medical Center, Des Moines, Iowa.
Arch Intern Med. 1993 Apr 26;153(8):957-61. doi: 10.1001/archinte.153.8.957.
To determine the natural course of the syndrome "subclinical hypothyroidism."
Prospective study of 30 subjects with "subclinical hypothyroidism," as documented precisely by normal serum thyroxine and triiodothyronine concentrations and high serum thyrotropin levels on three occasions at intervals of 2 to 3 weeks. The subjects were followed up for 4 to 15 years (mean, 8.2 +/- 2.3 years), with repeated determinations of thyroid hormone indices at intervals of 3 to 6 months.
Endocrinology Clinic at the Veterans Affairs Medical Center.
16 subjects developed definitive primary hypothyroidism within 3 months to 2 years, as reflected by a progressive rise in serum thyrotropin level with a gradual decline in serum thyroxine and triiodothyronine concentrations, with serum thyroxine levels falling to subnormal concentrations. In 14 of these subjects, primary hypothyroidism could be attributed to known etiologic factors, whereas in the remaining two the cause was not apparent. Persistently elevated serum thyrotropin with normal serum thyroxine and triiodothyronine concentrations following a cyclic pattern was observed in 14 subjects during the follow-up period. In 11 of these subjects, there was a history of non-radical surgery or conventional radiation therapy to the neck area, whereas in the remaining three subjects, no apparent cause could be identified.
"Subclinical hypothyroidism" is not always a forerunner of primary hypothyroidism. Two distinct populations evolve: (1) those with true preclinical or subclinical hypothyroidism, which may be predicted by the presence of one of the well-known etiologic factors responsible for onset of primary hypothyroidism, and (2) euthyroidism with reset thyrostat--a permanent state without a definitive progression to hypothyroidism, most probably secondary to a previous subtle insult to the thyroid gland.
确定“亚临床甲状腺功能减退症”综合征的自然病程。
对30例“亚临床甲状腺功能减退症”患者进行前瞻性研究，血清甲状腺素和三碘甲状腺原氨酸浓度正常，血清促甲状腺素水平在2至3周的间隔内三次升高，以此精确记录该病症。对这些患者进行了4至15年（平均8.2±2.3年）的随访，每隔3至6个月重复测定甲状腺激素指标。
退伍军人事务医疗中心内分泌科门诊。
16例患者在3个月至2年内发展为明确的原发性甲状腺功能减退症，表现为血清促甲状腺素水平逐渐升高，血清甲状腺素和三碘甲状腺原氨酸浓度逐渐下降，血清甲状腺素水平降至正常以下。其中14例患者的原发性甲状腺功能减退症可归因于已知病因，而其余2例病因不明。在随访期间，14例患者出现血清促甲状腺素持续升高，血清甲状腺素和三碘甲状腺原氨酸浓度正常，呈周期性变化。其中11例患者有颈部非根治性手术或传统放射治疗史，其余3例病因不明。
“亚临床甲状腺功能减退症”并不总是原发性甲状腺功能减退症的先兆。出现了两个不同的群体：（1）真正的临床前期或亚临床甲状腺功能减退症患者，可通过存在已知的导致原发性甲状腺功能减退症发病的病因之一来预测；（2）甲状腺调节功能重置的甲状腺功能正常——一种无明确进展为甲状腺功能减退症的永久状态，很可能继发于先前对甲状腺的轻微损伤。
