The clinical impact of subclinical hypothyroidism in Korean

Abstract

Patients with subclinical hypothyroidism (SHT) are common in clinical practice. However, clinical significance of SHT, including prognosis, has not been clarified. Based on it, management plan and treatment guideline of SHT could have been established. The aim of this study was to investigate the prognostic factors of SHT. We reviewed the medical records of Korean patients who visited the endocrinology outpatient clinic of Severance Hospital from January 2008 to September 2012. Among them, newly-diagnosed patients with SHT were selected and reviewed retrospectively. We compared two groups; SHT maintenance group and Spontaneously improved group. Between SHT maintenance group and Spontaneously improved group, initial thyroid-stimulating hormone (TSH) level was significantly different (p-value=0.030). In sub-analysis for subjects with TSH between 5-10 μIU/mL, Spontaneously improved group showed significantly lower anti-thyroid peroxidase antibody (TPO-Ab) titer than SHT maintenance group (p -value=0.038). In the aspects of lipid profiles, only triglyceride level, other than total cholesterol and low density lipoprotein cholesterol (LDL-C), was related with TSH level, that is, the severity of SHT. Diffuse thyroiditis (DT) on ultrasonography (US) only contributed to the severity of SHT, not to the prognosis. High-sensitivity C-reactive protein (hsCRP) and urine iodine excretion, generally regarded as possible prognostic factors, did not show any significant relation with the prognosis and severity of SHT. In conlusion, only initial TSH level was a definite prognostic factor of SHT. TPO-Ab titer was also a helpful prognostic factor for SHT with mildly elevated TSH. We could expect SHT patients with lower TSH level and lower TPO-Ab titer to be improved spontaneously to euthyroid state. Except TSH and TPO-Ab, we could not validate other biochemical prognostic factors in this retrospective study for Korean SHT patients. According to our experience, in clinical practice, we could explain to newly-diagnosed SHT patients that they have 50 percent chance to be improved to euthyroid after 10 months in its natural course. Considering this with other probable prognostic factors and clinical circumstances of the patient, we could also able to determine the management plan of the SHT patient.