Effect of infection with Spirometra erinacei plerocercoid on thyroid hormone in mice.

Young, male ICR mice were given tap water or distilled water containing 200 mg/l propylthiouracil (PTU) and were then infected with 10 plerocercoids of Spirometra erinacei to investigate the effect of plerocercoid infection on thyroid hormone in their hosts. Plerocercoid infection stimulated growth in PTU-induced hypothyroid mice as if they had never received PTU treatment: there were increases in weight in the liver, skeletal muscle, and spleen, as well as enhancement of the head and body length, in spite of a greater decrease in serum T4 levels than was observed in PTU-treated controls. Furthermore, the intact mice infected with plerocercoids showed a decrease in serum T4 levels as well as in the concentration of T4-binding globulin. These observations suggest that the growth stimulation and the decrease in concentrations of serum T4 and T4-binding globulin associated with plerocercoid infection in mice probably resulted from secretion of a growth hormone-like substance produced by plerocercoids of S. erinacei.