Thyroid

Sympathetic Innervation of Thyroid

The thyroid is located in the neck, and is a two sided gland responsible for releasing various hormones into the blood. It is predominantly controlled by Thyroid Stimulating Hormone (TSH) released by the pituitary, which in turn is regulated by the hypothalamus. This much has been known for some time. Additionally, the thyroid has sympathetic innervation, the role of which is less clear. The chemical iodide is absorbed by the thyroid, and converted into iodine, which is essential for proper thyroid function.

Schematic of Sympathetic Innervation of the Thyroid

Thyroid PET Scan After ETS

PET Scan of Neck After T2-T4 ETS

Flourodopamine PET scan of the human neck after T2-T4 sympathectomy. The butterfly-shaped outline indicates the approximate location of the thyroid. According to NIH’s David Goldstein, who took the scan, the lack of yellow-orange-red color within the outline indicates total sympathetic denervation of the thyroid. A normal scan is sought for comparison.

Thus we find evidence that the thyroid gland is innervated entirely between T2 and T4. More data are sought.

Rat Thyroid Study

What is the role of the SNS on thyroid function? Scientists at Northwestern University were puzzled, so they denerved rat thyroids on one side only. They injected a radioactive form of iodide known as 125I, so that the results on iodide uptake could be visualized.

“Unilateral superior cervical ganglion decentralization led to a reduction in thyroid weight, in 125I uptake by thyroid tissue, and in TSH-induced stimulation of 125I uptake in decentralized hemithyroids. These results suggest that sympathetic activity in thyroid contributes to gland enlargement and may modulate tissue responsiveness to TSH.” (Young et al., 2005).

Prediction: Thoracic sympathectomy will reduce iodide uptake by the thyroid. Empirical status: Confirmed in rats, unstudied in humans.

Prediction: Thoracic sympathectomy will reduce thyroid weight. Empirical Status: Confirmed in rats, unstudied in humans.

Iodine deficiency is associated with hypothyroidism (low thyroid function), thus:

Prediction: Thoracic sympathectomy will cause hypothyroidism. Empirical status: Unstudied.

Some of the symptoms of hypothyroidism are similar to some of the common anecdotal complaints of ETS patients. From the Mayo Clinic website, we gather:

Symptoms of Hypothyroidism

• Increased sensitivity to cold
• Constipation
• Pale, dry skin
• A puffy face
• Hoarse voice
• An elevated blood cholesterol level
• Unexplained weight gain
• Muscle aches, tenderness and stiffness
• Pain, stiffness or swelling in your joints
• Muscle weakness
• Heavier than normal menstrual periods
• Depression