Thyroid replacement for hypothyroidism
Since your thyroid gland is important for regulating metabolism, temperature, heart function, and many other things, when your body does not have enough thyroid hormone it needs to be replaced with medication.
- T4 (Levothyroxine, synthroid, levoxyl, Tirosint): Synthetic thyroid hormone replicant that comes in either brand or generic form. It is an exact copy of the hormone your body produces naturally, just that it is made in the lab (like insulin for diabetics that don’t make insulin anymore). T4 is the inactive form of thyroid hormone that gets converted to the active T3 by an enzyme in the body. It is long-lasting, taken once a day, and the more stable form of thyroid hormone and therefore is most common form of replacement. There are no side effects from the medication (since nothing foreign is being put in your body). However, your dose may need to be adjusted and therefore you could have symptoms of too little or too much hormone.
- T3 (Cytomel): active form of thyroid hormone. It is short acting, needs to be taken twice a day, and therefore the effects of missing a dose can be felt in short amount of time. There are also no real side effects since like T4, it is an exact copy of the hormone your body produces naturally, just that it is made in the lab (like insulin for diabetics that don’t make insulin anymore).
- T4/T3 pig thyroid hormone (Armour, Nature-thyroid). Although it may work for many people, not every batch has the same amount of thyroid hormone in it, so especially for cancer patients, this is not a good option. Additionally, since you are putting something foreign into your body, there can be allergic reactions and side effects.
One of the options for treating hyperthyroidism (and what is always at least initiated at the time of diagnosis) is medication. In the US, it is generally not utilized as a long-term option for patients with moderate to severe disease because it can be difficult to regulate and control, but is a good option for both mild disease and for patients initially to control symptoms before deciding on a more definitive treatment.
- Methimazole: most common and well-tolerated medication for treating hyperthyroidism. It prevents the conversion of T4 to T3 in the body. It is prescribed from 1-3x/day depending on the degree of hyperthyroidism. It has less side-effects than PTU, but it thought to be potentially harmful to a early developing fetus (first trimester). However, recent studies have shown that it is likely ok if a patient needs to be treated.
- PTU: similar to methimazole, it prevents the conversion of T4 to T3 in the body. Historically it has been preferred during the first trimester of pregnancy if a patient has newly diagnosed hyperthyroidism and pregnancy (and therefore does not have time for surgery or RAI) or had refused more permanent treatment before pregnancy. However, there are more side-effects than with methimazole.
- Aldosterone-antagonists (ie spironolactone; Eplerenone second line, more selective) to control high blood pressure and normalize levels of sodium, potassium, and water in the blood.
- Other anti-hypertensives can be added if needed and to decrease the spironolactone drug if there are side-effects.
- Low-salt diet
To manage Cushing’s syndrome, you may need medication to control the side effects of increased cortisol as well as drugs that attempt to inhibit cortisol production
- Medications to treat side effects: insulin for diabetes, anti-hypertensives for high blood pressure, bisphosphonates for osteoporosis.
- Steroidgenesis inhibitors (ketoconazole, metyrapone, mitotane): stop the adrenal glands from making too much steroids The second two have a larger side-effect profile; patients need close monitoring with all drugs.