June 25, 2001

According to findings reported at the 83rd Annual Meeting of the Endocrine Society in Denver, Colorado last week, it is more accurate to evaluate peripheral organs for levels reflective of the the severity of hypothyroidism rather than blood tests for thyroid stimulating hormone (TSH) levels.

The findings were reported by Swiss doctor Christian Meier, from the University Hospital in Basel.

Serum thyroid-stimulating hormone (TSH) is the most sensitive routine test for screening and early diagnosis of hypothyroidism, according to the researchers. However, no data are available for the evaluation of TSH as a measure for the degree of hypothyroidism at the tissue level.

Dr. Meier's studies looked at TSH levels, investigating 58 women who had full-scale hypothyroidism, and 153 women who were mildly hypothyroid, with elevated TSH levels but normal T4 levels. In all women, they looked at such clinical markers that show evidence of hypothyroidism at the tissue level, including reflex responses of the ankle, total cholesterol, low-density lipoprotein (LDL) levels, and circulating creatine kinase, total cholesterol and low-density lipoprotein (LDL)-cholesterol levels.

The most hypothyroid patients had no correlation between these tissue markers and the TSH levels. Free thyroxine (known as Free T4) levels, however, did correlate with the metabolic assessment tests. What they found was that worsening tissue hypothyroidism, which could be evidenced by worsening of ankle reflex test values, did not show a significantly corresponding increase in TSH.

The researchers told DG News, "Serum TSH is a poor test to estimate the severity of tissue hypothyroidism. This is in direct contrast to the generally accepted view that TSH is the best and most reliable screening test for assessing routine thyroid function."