The central nervous system (CNS) can be greatly affected by a thyroid disorder. The CNS reacts to both too little and too much thyroid hormone. In many cases, the neurologic manifestations occur in conjunction with the systemic features of thyroid disease and may be noted only incidentally. However, symptoms and signs of neurologic dysfunction may be the presenting feature in some patients and can contribute significant disability. Most of these complications are partially or fully responsive to thyroid replacement therapy in the majority of cases but for some Thyroid dysfunction related neuropathy can become a life long struggle.
Hypothyroidism
Hypothyroidism — a condition in which your thyroid gland doesn’t produce enough thyroid hormone — is an uncommon cause of peripheral neuropathy.
Peripheral neuropathy is damage to your peripheral nerves — the nerves that carry information to and from your brain and spinal cord (central nervous system) and the rest of your body, such as your arms and legs.
Peripheral neuropathy may be caused by severe, long-term, untreated hypothyroidism. Although the association between hypothyroidism and peripheral neuropathy isn’t fully understood, it’s known that hypothyroidism can cause fluid retention resulting in swollen tissues that exert pressure on peripheral nerves.
One of the more common areas this occurs in is the wrists, because the nerve serving the hands goes through a “tunnel” of soft tissue, which can swell, pressing on the nerve, resulting in carpal tunnel syndrome. The vast majority of carpal tunnel syndrome cases are not due to hypothyroidism, but this would be the most likely area for this to occur with hypothyroidism.
Signs and symptoms of peripheral neuropathy may include pain, a burning sensation, or numbness and tingling in the area affected by the nerve damage. It may also cause muscle weakness or loss of muscle control.
Without thyroid hormone, you can’t think as sharply. You may feel a little foggy, which can affect your ability to drive and make decisions.
Recent studies have linked hypothyroidism and Hashimoto’s disease with accelerated brain degeneration and development of Parkinson’s, Alzheimer’s and Huntington’s disease.
Hyperthyroidism
Hyperthyroidism is a condition of abnormally high thyroid hormone levels, which causes all bodily functions to become sped up (hyper-metabolism). Muscle reflexes are hyper-reactive, meaning there is abnormal muscle tension in response to brain-nerve signals. This can result in the adverse effect following physical activity, of severe muscle weakness. Some patients may also experience episodes of muscle paralysis and/or muscle deterioration. Neurological symptoms that accompany hyperthyroid conditions are sometimes referred to as “thyrotoxic myopathy” but will improve significantly with treatment to reduce thyroid hormone levels and treatment for symptoms of an overactive metabolism via anti-thyroid drugs and beta-blockers.
Hyperthyroidism actually begins slowly and the symptoms can be mistaken for a low end irritability and anxiety.
References:
http://sjccfthynet.blogspot.com/2011/02/neuropathy-symptons-and-thyroid-disease.html
https://www.webmd.com/women/features/low-thyroid-complications#2
