[The effect of levothyroxine on the proliferative activity of the thyroid follicular cells]

Pharmacological treatment of non-toxic nodular goitre with levothyroxine has caused a discussion about its effectiveness and safety. The aim of the study was to examine the influence of levothyroxine on the proliferative activity of the thyroid follicular cells.

Cytological material was obtained from 32 euthyroid females, aged 34-69 years, by USG-guided Fine-Needle Aspiration Biopsy (FNAB), before and after 6 months treatment with levothyroxine. The patients were divided into 2 age groups: up to 45 years (14 patients) and above 45 years (18 females). Proliferative activity of the follicular cells was assessed by the proliferative index (PI), representing the percentage of follicular cells with positive reaction with the antibody Ki-67. Microscopic evaluation was carried out using morphometric computer system MicroImage InCD UDF (Olympus).

After 6-months of treatment IP values decreased significantly in both groups studied (8.59 +/- 3.07 vs 6.51 +/- +/- 1.91; p < 0.001 in females aged < 45 years and 7.72 +/- 1.83 vs 5.09 +/- 1.51; p < 0.001 in the older group).

Our results indicate that levothyroxine has an influence on the proliferative activity of the thyroid follicular cells, particularly in post-menopausal women.