Three basic patterns of changes in serum thyroid hormone levels in graves' disease during the one-year period after radioiodine therapy

ABSTRACT

Was to clarify the characteristic patterns of the thyroid hormonal changes in Graves' disease during the one-year period after [131]I therapy considering that few serial hormonal data during this period are available in the literature. The levels of serum T[3], T[4] and FT[4] before and during one year were plotted as a function of time in 86 therapy courses of 70 patients without subsequent antithyroid or steroid therapy. 35 euthyroid, 6 hypothyroid and 29 hyperthyroid states were obtained during one year after therapy. Although individual patients had individual hormonal changing patterns, 3 common basic patterns were observed from baseline to one month [early] and thereafter [late], respectively. The early patterns were a decrease in 54 [77%], a minimum change in 8 [11.5%] and an increase in 8 [11.5%]. The late patterns were a stable state after an initial decrease with a bottom followed by an increase [valley pattern] in 47 [67%], a stable state after an initial increase with a peak followed by a decrease with a bottom and a subsequent re-increase [mountain pattern] in 12 [17%] and a late stable state after a gradual slow decrease without an obvious bottom near or till one year [downhill pattern] in 11 [16%]. The bottom level and the degree of hormonal recovery from the bottom determined the stable euthyroid, hypothyroid or hyperthyroid state in 49 [86%] of 59 with the valley or mountain pattern. Most of the bottom levels [81%] and transient abnormal changes including transient hypothyroidism [93%, 13/14], peak or hyperthyroidism [85%, 11/13] and euthyroidism [67%, 10/15] appeared within 6 months. The posttherapeutic stable euthyroid, hypothyroid or hyperthyroid state could be judged from the hormonal patterns in 57% [39/68] from 2.5 to 6 months, in 18% [12/68] from 6 to 9 months and in 25% [17/68] thereafter. Although the changes in thyroid hormones are not constant in Graves' disease during one year after [131]I therapy, there are three basic patterns; valley, mountain and downhill patterns from one month after therapy. The post-therapeutic stable state can be judged by the hormonal level recovered from the bottom in most patients