Thyroid function includes evaluating whether I am hypothyroid (low in thyroid hormone) or hyperthyroid (high in thyroid hormone) and what signs and symptoms I will likely experience. Patients diagnosed with hypothyroid or hyperthyroid disease are managed with medications and go on to live long, prosperous lives.
The endocrine system is organized as a hierarchy of glands. The pituitary gland is the master gland. It is a small gland that controls several other hormone glands, including the thyroid gland. The thyroid gland is located in the lower part of the neck, below the Adam’s apple (larynx) and straddling the trachea (windpipe). The thyroid gland produces two hormones, T3 and T4, that regulate people’s energy and metabolic needs. The hypothalamus (in the brain) is the command center. The hypothalamus directs the pituitary to signal the thyroid to produce thyroid hormone when serum levels are low, or to shut off its release when serum levels are elevated.
According to the National Institutes of Health, approximately 5% of Americans aged 12 or older have hypothyroidism, while about 1% have hyperthyroidism. Thyroid diseases are more common in women, with rates 5 to 10 times higher than in men. The rate of effective treatment has risen from 9.6% in 2012 to 11.7% in 2019.
The common signs and symptoms of hypothyroidism include fatigue, lethargy, weight gain, cold intolerance, skin and hair changes, musculoskeletal pain, brain fog, constipation, menstrual and fertility changes, a puffy face, hoarseness, and bradycardia (low heart rate). The common signs and symptoms of hyperthyroidism include a rapid heart rate (tachycardia), palpitations, arrhythmias, weight loss, increased sweating, brittle hair, moist skin, tremors, muscle weakness, increased bowel movements, swelling of the thyroid gland (goiter), protruding eyes (exophthalmos), anxiety, nervousness, irritability, difficulty concentrating, and insomnia.
The treatment goals for hypothyroidism are to correct the metabolic manifestations and to supplement or replace T4 hormone medication to treat low T4 levels. The treatment goals for hyperthyroidism are to inhibit the overproduction of thyroid hormone using antithyroid medication. The definitive treatment for hyperthyroidism is radioactive iodine, which completely eradicates all thyroid function. The patient is initiated on T4 therapy to maintain thyroid hormone levels within the therapeutic range.
Risk factors for hypothyroidism include being female, age over 60 years, and a family history of thyroid disease. According to the American Thyroid Association (ATA) guidelines, treatment is initiated with full anticipated full replacement doses of T4 (thyroid hormone). Four weeks after starting T4, a serum T4 level is obtained to inform the endocrinologist whether a dose change is needed. Clinical benefits of thyroid medication begin within 3-5 days and level off in 4-6 weeks. The standard of care is to initiate levothyroxine (T4). Common trade names for levothyroxine include Synthroid, Ermeza, Levothroid, Levoxyl, and Unithroid. Levothyroxine side effects include fast heart rate (tachycardia), chest pain, tremors, nervousness, insomnia, sweating, heat intolerance, weight loss, and diarrhea. Another thyroid hormone medication used in clinical practice is liothyronine (T3). If the endocrinologist feels that the patient is not adequately controlled on levothyroxine alone, liothyronine is added to the patient’s medication regimen. The trade name for liothyronine is Cytomel. Side effects of liothyronine are the same as those of levothyroxine.
In my interactions with endocrinologists over these many years, I have observed alternative forms of T3 and T4 thyroid hormone medications being prescribed. Two of the alternative thyroid hormone replacement medications are organic. Desiccated pig glands are manufactured into tablets containing T3 and T4. The trade names of this medication are Amour Thyroid, Westhroid, Porcine Thyroid, and Nature-Thyroid. Liotrix (Thyrolar) is a synthetic combination of T3 and T4 in a 4:1 ratio. Thyroid USP (NP Thyroid) is derived from pig thyroid glands that contain T3 and T4. The FAA’s requirements for levothyroxine, liothyronine, desiccated thyroid, liotrix, and Thyroid USP dosing are based on Special Issuance if not CACI-qualified.
Risk factors for hyperthyroidism include being female, age over 60, a family history of thyroid disease, and being a type I diabetic (patients requiring insulin therapy only). According to the ATA hyperthyroid treatment guidelines, antithyroid medications are prescribed to inhibit the overproduction of thyroid hormone. Propylthiouracil, carbimazole, and methimazole (Tapazole) work by inhibiting the production of T4 and T3. Antithyroid medications produce a gradual reduction in thyroid hormone levels over 2-8 weeks or longer. Antithyroid medication dosing is titrated every 4 weeks until thyroid hormone levels normalize. Methimazole is the first-line medication for hyperthyroidism because it is more potent and is taken once a day. Propylthiouracil is considered second-line therapy if methimazole does not control the patient’s hyperthyroidism. Side effects of methimazole, carbimazole, and propylthiouracil include skin rashes, nausea, and joint pain, which may occur in 1-5% of patients. Serious but rare side effects include severe liver damage and agranulocytosis (low white blood cells), with an occurrence rate of 0.2-0.5%. The FAA’s requirements for propylthiouracil are based on a status report and the absence of adverse side effects. For carbimazole therapy, there are no FAA-based restrictions. FAA approval for Tapazole therapy for hyperthyroidism requires a detailed medical evaluation, reviewed on a case-by-case basis.
That little bowtie-shaped thyroid gland in our neck plays a major role in regulating our metabolism and energy levels. When the thyroid gland becomes overactive or underactive, producing too much or too little thyroid hormone, your body will let you know. If you notice symptoms of hypothyroidism or hyperthyroidism, contact your primary healthcare professional sooner rather than later. You are likely to be referred to an endocrinologist, an expert in the field. All hypothyroid and hyperthyroid medications are available in generic form. Use the cost savings from GoodRx when your pharmacist fills your prescription. Be well and fly safe.
