Influence of sympathetic denervation of the thyroid by superior cervical ganglionectomy on the growth processes in the gland in basal conditions and after hemithyroidectomy.

The aim of the present study has been to examine the effects of superior cervical ganglionectomy (SCGx) on the hypertrophic (thyroid lobe weight) and hyperplastic (thyroid mitotic activity) response of the rat thyroid gland in basal conditions or after hemithyroidectomy (hemiTx), both being assessed 14 days after the surgeries. It has been shown that: 1) Ipsilateral and/or bilateral SCGx brought about the growth (both hypertrophy and hyperplasia) of thyroid lobes in the animals with intact thyroid; the strongest hypertrophic reaction occurred after ipsilateral SCGx and the strongest hyperplastic response followed bilateral SCGx. 2) Unilateral SCGx, when performed ipsilaterally to the remaining thyroid lobe after hemiTx amplified the hypertrophic, but not hyperplastic response of this lobe. Both contralateral and bilateral SCGx had no effect on the hypertrophy of the remaining thyroid lobe. Unexpectedly, both bilateral and contralateral SCGx exerted the suppressive effect on the hyperplastic response of the thyroid lobe following hemiTx. These results indicate that the sympathetic innervation plays an important role in the control of thyroid growth of intact animals and/or after hemiTx.