Thyroid Issues

The thyroid is a vital gland that secretes a hormone (thyroxin) that helps regulate body metabolism. In excess quantities (hyperthyroidism), it can increase the heart rate or produce cardiac problems, affect respiratory rate, decrease body weight and even interact with the central nervous system. Symptoms of hyperthyroidism also include discomfort or anxiety. Cardiac effects include tachycardia (fast rate), serious dysrhythmias and heart failure. Hyperthyroidism also causes muscular weakness and periodic paralysis in individuals of Chinese descent. Lower-than-normal levels of thyroxin (hypothyroidism) may cause fatigue and slow or absent reflexes. Hypothyroidism is also characterized by a slow heart rate and slow metabolism; it may cause heart failure.

The thyroid gland's output can be controlled by medication, radiation, radioactive iodine or surgery: this is to reduce the function of the thyroid, or it can reduce the amount of hormone released. Once the hormone level has been reduced to within the normal range (assessed by blood tests), and the signs and symptoms of hyperthyroidism have resolved, then a diver with a thyroid condition may resume diving. Note: This assumes, however, that the diver has no other major health problems and the diver can achieve a suitable level of physical performance.

Individuals who are treated (by medication, radiation, radioactive iodine or surgery) may become truly hypothyroid (have reduced thyroid function) and may require supplemental thyroxine (eg. Synthroid®) to actually raise their hormone level back into the normal range. It is vital for all individuals with thyroid ailments to have their thyroid function measured regularly by blood test. This can help check for hypo- or hyperthyroidism and can indicate the efficacy of treatment.

Fatigue sometimes occurs as a side effect of therapy: this may be a hurdle for a return to diving. Fatigue may lead to a decreased level of fitness, thus limiting endurance and stamina.

Fitness and Diving:
Participation in recreational scuba diving is usually considered unsafe for individuals with hyperthyroidism. In untreated hyperthyroidism, thyroxin can be released in large quantities, causing debilitating symptoms for the submerged diver. Don't dive without treatment.

Medication Used in Treatment:
Synthroid has no known interaction with decompression illness.

Additional Information:
American Thyroid Association
Australian Thyroid Foundation