Reduced thyrotropin in euthyroid goitrous patients suggesting subclinical hyperthyroidism.

BACKGROUND: Subclinical hyperthyroidism, a biochemical finding of low serum thyrotropin (TSH) with the serum levels of thyroxine (T4) and triiodothyronine (T3) within the reference range, could easily be ignored by clinicians, as it, usually, does not manifest with any thyroid specific symptoms. It is of two types: endogenous and exogenous. However, patients with the findings of low TSH, normal T4 and T3 develop some abnormalities in the cardiovascular system, such as atrial fibrillation, increase in left ventricular mass and diastolic dysfunction. It is believed that treatment intervention may reduce or halt the progression of the cardiac abnormalities. The main objective of the study was to determine how frequent subclinical hyperthyroidism was occurs and to serve as a reminder to the existence of the disorder.

METHODS: It was a hospital-based study carried out at the Jos University Teaching Hospital (JUTH). Consecutive clinically euthyroid goitre patients attending the outpatient department of JUTH, were studied for various parameters including TSH, T4 and T3 The serum concentrations of T4 and T3 were determined by enzyme-linked immunosorbent assay (ELISA) technique. The serum TSH concentration was estimated using a 2nd generation ELISA technique.

RESULTS: 98 patients participated in the study. Nine patients had non-specific symptoms not referable to the thyroid and found to have high levels of thyroid hormone concentration with depressed TSH and were excluded from further analysis, while 7 had subclinical hyperthyroidism giving a prevalence rate of 7.9% among these clinical euthyroid goitre patients. The subjects with this condition were mainly above 60 years of age and mainly had long-standing goitre.

CONCLUSION: Endogenous subclinical hyperthyroidism was present in 7.9% of these clinically euthyroid goitre patients mainly 60 years and above, with long-standing goitre. This high prevalence rate calls for high index of suspicion as this condition is associated with morbidities that can raise mortality.