Fly Well: Float like a butterfly, sting like a bee

An endocrine organ, the thyroid makes and releases hormones that act like a throttle. When more thyroxine is needed, a chemical messenger from the brain encourages the gland to firewall the throttle by releasing thyroid stimulating hormone (TSH). Conversely, when circumstances dictate less throttle is required, less TSH is released, thereby retarding production.

In hypothyroidism, too little thyroxine is produced and the resulting symptoms inspire thoughts of an underpowered aircraft wallowing along on the edge of a stall. The patient is lethargic, constipated, is not hungry, is overweight, moves slowly, has dull hair and skin, has muscle aches, and cannot tolerate cold weather. Goiter (swollen neck) results from TSH trying to force the failing gland to get its act together. Hypothyroidism is one of the most-diagnosed thyroid conditions.

An iodine-poor diet can lead to hypothyroidism, and Chinese Emperor Shen Nung’s prescription for iodine-rich seaweed dates back more than 4,000 years. Leonardo Da Vinci knew of thyroid disorders and painted subjects with enlarged glands, and seventh-century paintings show saints and other religious figures with goiter. Hashimoto’s thyroiditis is a condition in which the body mistakes the thyroid for a foreign tissue and damages the organ. Therapy consists of prescribing levothyroxine, a hormone-replacement drug. For pilots applying for a medical certificate, hypothyroidism may be a Condition AMEs Can Issue (CACI), if controlled as indicated by TSH levels. If well treated, pilots can self-assess and report at their next medical if CACI qualified. If not suitable for CACI, the AME will defer to the FAA for a decision that will most likely result in a special issuance.

On the other hand, or gland, if your thyroid makes too much hormone, think stuck throttle. Heat will be generated and poorly tolerated, appetite is ravenous, diarrhea predominates, weight falls off, tremors are evident, heart rate is rapid and possibly out of rhythm, and anxiety and difficulty sleeping complete the not-so-pretty picture. Graves’ disease, which the Bushes have, is the most common cause of this condition and often also induces a wide-staring gaze, which is quite specific and hard to miss. Again, diagnosis is not difficult either clinically or with blood tests.

Treatment involves reducing gland activity by blocking iodine uptake with medications, surgically excising a chunk of gland, or having the patient imbibe radioactive iodine which, over the course of weeks or months, is preferentially taken up by the thyroid, killing it. Thereafter, the patient must take hormone replacement therapy as in hypothyroidism. Hyperthyroidism can be an AME-assisted special issuance (AASI). “Decision Considerations—Aerospace Medical Dispositions, Item 48. General Systemic—Endocrine Disorders” in the FAA’s Guide for Medical Examiners describes how AMEs manage hypo- and hyperthyroidism.

Anomalies of thyroid structure can either be benign or malignant. If you find a lump in your neck, advance your throttle and land at a doctor’s office with expedition. A physical examination and ultrasound will ascertain if it is solid or fluid-filled and whether using a needle will suffice or surgical excision is required. Thyroid cancers are the most common endocrine malignancy but comparatively rare. They come in many forms: papillary, follicular, medullary, and anaplastic, the last of which is the most aggressive. It is important to ascertain the stage of given tumor and whether it has spread, but many are eminently treatable if caught early. As Ebert so bravely documented, the course can be long and difficult. As so often in medicine, early diagnosis provides a competitive advantage. For medical certification, tumors require status report from treating doctors, operative and pathology reports, and TSH levels. If malignant, special issuance is required.

Of the many factors associated with thyroid cancer, environmental ones provoke the most heated debates. When Japan’s Fukushima nuclear plant was crippled, radioactive isotopes were released into the atmosphere, including Iodine-131, the same type used to destroy an overactive gland. Other elements like cesium and strontium, floating like a butterfly on global winds, might also sting like a bee.