Re: Повышеннный ТТГ и нормальные Т3, Т4
#16Вот тут нашел попытку ответа на свой вопрос - почему считается, что ТТГ высокий - плохо, если при этом гормоны удается железе выдать в пределах нормы. Но логику этого ответа не совсем понял.
http://www.ncbi.nlm.nih.gov/pubmed/11600507
“One of
the myths that surrounds subclinical hypothyroidism is that
the laboratory profile of an elevated serum TSH and normal
free thyroid hormone levels really represents “compensated
hypothyroidism.” The reasoning behind this idea is that,
since the circulating levels of thyroid hormones are within
the normal range with only the serum TSH being elevated,
the affected subject is really euthyroid because the increased
TSH is stimulating and driving the thyroid gland to produce
normal thyroid hormone levels. Certainly, elevated serum
TSH levels do stimulate even a diseased thyroid gland to
produce and release more thyroid hormone. However, as
long as the serum TSH level remains elevated, the thyroid
hormone levels are not truly normal for that individual. The
clearance kinetics of thyroid hormones and TSH from the
circulation actually make such a conclusion inescapable. Because the half-life of T4is 7 d and that of T
3is 1 d, the serum
TSH, which has a half-life of less than 1 h, would certainly
be expected to return to normal if thyroid hormone levels
were, indeed, normal for that individual. An elevated TSH
in an individual patient, thus, means that the circulating
thyroid hormone concentrations are insufficient, with a few
rare exceptions (TSH-secreting tumors, thyroid hormone resistance syndromes).”