Vagosympathetic imbalance induced thyroiditis following subarachnoid hemorrhage: a preliminary study

Introduction: This preliminary study evaluates the possible responsibility of ischemia-induced vagosympathetic imbalances following subarachnoid hemorrhage (SAH), for the onset of autoimmune thyroiditis.

Methods: Twenty-two rabbits were chosen from our former experimental animals, five of which were picked from healthy rabbits as control (nG-I=5). Sham group (nG-II=5) and animals with thyroid pathologies (nG-III=12) were also included after a one-month-long experimental SAH follow-up. Thyroid hormone levels were measured weekly, and animals were decapitated. Thyroid glands, superior cervical ganglia, and intracranial parts of vagal nerve sections obtained from our tissue archives were reexamined with routine/immunohistochemical methods. Thyroid hormone levels, hormone-filled total follicle volumes (TFVs) per cubic millimeter, degenerated neuron density (DND) of vagal nuclei and neuron density of superior cervical ganglia were measured and statistically compared.

Results: The mean neuron density of both superior cervical ganglia was estimated as 8230±983/ mm3 in study group animals with severe thyroiditis, 7496±787/mm3 in the sham group and 6416±510/mm3 in animals with normal thyroid glands. In control group (group I), T3 was 107±11 μg/dL, T4: 1,43±0.32 μg/dL and TSH <0.5, while mean TFV was 43%/mm3 and DND of vagal nuclei was 3±1/mm3. In sham group (group II), T3 was 96±11 μg/dL, T4: 1.21±0.9 μg/ dL and TSH>0.5 while TFV was 38%/mm3 and DND of vagal nuclei was 13±4. In study group, T3 was 54±8 μg/dL, T4: 1,07±0.3 μg/dL and TSH >0.5, while TFV was 27%/mm3 and DND of vagal nuclei was 42±9/mm3.

Conclusion: Sympathovagal imbalance characterized by relative sympathetic hyperactivity based on vagal insufficiency should be considered as a new causative agent for hypothyroidism.