Congenital goitrous hypothyroidism: discordant systolic time intervals, pituitary and peripheral responses to high daily doses of T4 or T3 therapy

Abstract

Left ventricular performance was studied by a noninvasive technique through the measurement of the systolic time intervals (total eletromechanical systole, left ventricular ejection (LVET) time, preejection period (PEP) and PEP/LVET ratio (Systolic Quotient) in 8 young adults with congenital goitrous hypothyroidism. All subjects showed lengthening of PEP, shortening of LVET and an increased PEP/LVET ratio associated with low serum T3 and T4, an exaggerated TSH response to TRH, high levels of serum cholesterol, triglycerides and carotene. They were treated with increasing L-T4 at monthly intervals (100, 200 and 400 micrograms daily), followed by L-T3 (50 and 200 micrograms daily) after stopping medication for another month. Systolic time intervals and the systolic quotient promptly reversed to the normal range with physiologic L-T4 (100 micrograms) or L-T3 (50 micrograms) replacement, but the TSH peak response to TRH was still present and exaggerated. Further reductions of the systolic quotient occurred with 200 micrograms L-T4, but not with supraphysiological doses (400 micrograms L-T4 or 200 micrograms L-T3) of thyroid hormones. The highest dose of L-T3 (200 micrograms/day) induced a significantly lower mean systolic quotient than 400 micrograms L-T4 daily, while 5 patients still had a significant TSH response to TRH. This was interpreted as discordant pituitary and cardiac response to L-T3 and L-T4 therapy. Serum cholesterol and triglycerides were considered as very sensitive index of thyroid hormone peripheral action. These had a significant positive correlation with changes in the left ventricular performance. Serum carotene, although decreasing significantly with L-T4 or L-T3 treatment, had no significant correlation with the systolic quotient.(ABSTRACT TRUNCATED AT 250 WORDS)