Interaction entre Estradiol et Lévothyroxine et liothyronine

Hypothyroidism Estrogen administration leads to increased thyroid-binding globulin (TBG) levels.

Patients with normal thyroid function can compensate for the increased TBG by making more thyroid hormone, thus maintaining free T 4 and T 3 serum concentrations in the normal range.

Patients dependent on thyroid hormone replacement therapy who are also receiving estrogens may require increased doses of their thyroid replacement therapy.

These patients should have their thyroid function monitored in order to maintain their free thyroid hormone levels in an acceptable range.

Increased thyroid-binding globulin (TBG) levels leading to increased circulating total thyroid hormone levels as measured by protein-bound iodine (PBI), T 4 levels (by column or by radioimmunoassay) or T 3 levels by radioimmunoassay.

Estrogen, Oral Contraceptives — Estrogens tend to increase serum thyroxine-binding globulin (TBg).

In a patient with a nonfunctioning thyroid gland who is receiving thyroid replacement therapy, free levothyroxine may be decreased when estrogens are started thus increasing thyroid requirements.

Therefore, patients without a functioning thyroid gland who are on thyroid replacement therapy may need to increase their thyroid dose if estrogens or estrogen-containing oral contraceptives are given.