By Bobbie Fisher
The thyroid gland is often described as butterfly shaped, but the comparison doesn’t stop there. Although relatively small (.03-.04 grams), the average butterfly provides a wide range of environmental benefits, including pollination and natural pest control (in addition to being a food source itself), making it one of nature’s workhorses. Similarly, despite its own relative small size (20-60 grams), the human thyroid produces and stores the hormones that regulate metabolism and influence the function of every cell, tissue and organ in the body, including the heart, the brain, the liver, kidneys, intestines and skin.
For all its importance, the butterfly is a fragile and delicate creature, susceptible to many natural predators and having a very short lifespan. The thyroid, while not as fragile, is likewise subject to a variety of conditions, many of which are complex, and can be challenging to understand.
“Thyroid disease is very common,” says David C. Lieb, MD, an associate professor of internal medicine and program director of the Endocrinology Fellowship Program at Eastern Virginia Medical School. More than 12 percent of the US population will develop a thyroid condition at some point during their lives. That is, an estimated 20 million Americans have some form of thyroid disease. “As many as 60 percent of them are unaware of their condition,” Dr. Lieb says, “which could be too much or too little thyroid hormone, a thyroid nodule or thyroid cancer. And untreated thyroid disease can put patients at risk for serious conditions, such as cardiovascular disease, osteoporosis, infertility, depression, mental slowing and others.”
Women are five to eight times more likely to have hypothyroidism. “Despite the research, we still haven’t figured that out,” says Jennifer Wheaton, DO, an endocrinologist with Bayview Physicians Group. However, hypothyroidism is often caused by an autoimmune process (termed ‘Hashimoto’s thyroiditis’). For unclear reasons, women are often more likely to develop autoimmune disease compared with men. “It’s also worth noting that the symptoms of menopause are almost identical to the symptoms of hypothyroidism: fatigue, weight changes, mood swings, difficulty sleeping. I’ve seen women who experienced these symptoms and assumed they were caused by menopause, and thus their diagnosis was delayed.” That happens less these days, she adds, as physicians and patients are more aware of hypothyroidism and its symptoms.
TSH Screening.
The routine test is the thyroid stimulating hormone, or TSH, taken from a blood sample. It’s considered the gold standard. From the American Thyroid Association:
A high TSH level indicates that the thyroid gland is failing because of a problem that is directly affecting the thyroid (primary hypothyroidism). The opposite situation, in which the TSH level is low, usually indicates that the person has an overactive thyroid that is producing too much thyroid hormone (hyperthyroidism). Occasionally, a low TSH may result from an abnormality in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid (secondary hypothyroidism). In most healthy individuals, a normal TSH value means that the thyroid is functioning normally.
Because thyroid disease is so common, it can be challenging to determine exactly who needs to be screened, and when. “When something is so prevalent, you could easily say that everyone should be screened,” Dr. Lieb says. The United States Public Health Service Task Force argues there is insufficient evidence to screen anybody, while the American College of Physicians says every woman over 50 should be screened. The American Thyroid Association guidelines indicated screening for anyone at risk.
Additionally, Dr. Wheaton explains, the TSH number can fluctuate: “There are definitely things that can affect it, especially if the patient is sick. There’s an entire condition called euthyroid sick syndrome, which results in abnormal thyroid function tests during a nonthyroidal illness in patients without pre-existing hypothalamic-pituitary or thyroid disorder.” When the patient recovers from the nonthyroidal illness, she says, the abnormalities resolve.
Similarly, in thyroiditis, when the thyroid is being destroyed by a viral infection, it will release a substantial amount of thyroid hormone because the cells are breaking apart as they’re dying, Dr. Lieb explains: “So these patients become hyperthyroid for a period of time, and then it peaks, and they come back to normal. But sometimes rather than remaining at normal levels, they can get too low and become hypothyroid, requiring thyroid hormone.”
There are other factors that can result in abnormal TSH results, as well – even a patient’s (non)compliance with a thyroid hormone replacement regimen before testing.
Fortunately, most thyroid diseases can be managed with medical attention.
Most of the time, once patients have thyroid disease, they have it for life; however, because it’s an autoimmune disease, it can sometimes resolve itself. “We more commonly see that in hyperthyroidism due to Graves’ disease,” Dr. Wheaton says, “and some patients with Graves’ can be treated for a year or two with medication to normalize their thyroid, and then go into a kind of remission with thyroid levels that will stay normal on their own.”
With hyperthyroidism, treatment options include anti-thyroid medications – propylthiouracil and methimazole – but because of their side effects, they are not recommended for life-long use, particularly at the higher levels. Another option is radioactive iodine ablation, which causes the thyroid gland to shrink and thyroid activity to slow down. One of the sequelae of radioactive iodine is that it can cause hypothyroidism, requiring treatment for that condition.
The standard treatment for patients with hypothyroidism, whether as a result of radioactive iodine for hyperthyroidism or of Hashimoto’s disease, is to replace the thyroid hormone the body can no longer make with a daily dose of levothyroxine. To ensure the patient is receiving the proper dose, levels are monitored after initiating treatment and whenever the dose is changed.
Goiter is another presentation of thyroid disease that requires skill to diagnose. A patient can have a goiter with a normal TSH, or a goiter with hypothyroidism or a goiter with hyperthyroidism, or a goiter with several nodules that are inactive or a goiter with nodules that are producing too much thyroid hormone. In some cases, a patient with nodules and Graves’ disease may have a goiter so large that it interferes with swallowing or breathing. In this case, surgical removal of the thyroid is indicated.
There has been an increase in both the incidence of thyroid nodules and the incidence of thyroid cancer in the United States over the last five to 10 years. Thyroid nodules are generally incidental findings, as the majority are asymptomatic. They are usually diagnosed when a patient has a head or chest CT scan or x-ray. “Thyroid nodules are more common as patients age,” Dr. Lieb says. “In fact, if we did an ultrasound on everybody in their 60s and 70s, at least half of them would have nodules.”
The determination at that point is how best to proceed, particularly in light of the fact that fully 90 percent of thyroid nodules are benign. “We’ll do a biopsy to determine whether there is cancer,” Dr. Lieb says, “and do another ultrasound at six months to see if it’s changing. And we’ll check thyroid labs to see if it’s overactive, and treat accordingly.”
Thyroid cancer is one of the fastest rising cancers, especially in women, but mortality from thyroid cancer has not increased; the rate of death is actually very low. Of the four types of thyroid cancer – papillary, medullary, anaplastic and follicular – papillary is the most common, Dr. Wheaton explains. “The majority of patients with papillary cancer have their thyroid removed, maybe radioactive ablation afterward, and they do well,” she says, emphasizing that it always depends on the patient.
Medullary thyroid cancer is a more aggressive disease, with a higher mortality rate, tending to be a genetic cancer that has often metastasized before it’s found. Similarly, anaplastic thyroid cancer, which claimed the life of Supreme Court Justice William Rehnquist, is very aggressive and almost always fatal.
When Surgery is Indicated.
With a diagnosis of cancer, removal of the entire thyroid is indicated, as well as some of the surrounding lymph nodes, says Rebecca Britt, MD, a fellowship trained general and laparoscopic surgeon and associate professor at Eastern Virginia Medical School. “From a recovery standpoint, most patients do extremely well with thyroid surgery,” Dr. Britt says. “Our most common complications are low calcium after surgery. In about three percent of surgeries, patients experience recurrent laryngeal nerve injury, or hoarseness, which is permanent less than one percent of the time.”
“It’s a very delicate operation,” explains Doris Quintana, MD, a general and endocrine surgeon with Riverside Surgical Specialists, who did additional training in thyroid and parathyroid. “Keen attention to the finest details really makes a difference in how the patient does, particularly because of the presence of the four small parathyroids that are crucial to survival.”
The surgery is traditionally done through a transverse incision across the front of the neck. Today, surgeons like Dr. Britt and Dr. Quintana can perform the operation with much smaller scarring than in previous years, but for some female patients, they both agree, there is a concern about any scar on the neck. In some cultures, for instance, where any imperfection is considered to render a woman unmarriageable, some surgeons are doing the procedure endoscopically, with tiny incisions in the axilla or underarms, or even around the areola of the nipple. “A tunneling device is then used to come up to the neck,” Dr. Quintana says. “It’s been done some in this country as well, but not extensively.”
Sometimes, Dr. Britt explains, the diagnosis of cancer isn’t easily made. “We do surgery because despite the workup we’ve done, we can’t tell for sure whether something is a cancer or not,” she says. “Some patients have a nodule or nodules, and when we biopsy them, they come back with follicular cells. Frequently those are not cancer, but in order to definitively diagnose, we have to take the whole lobe of the thyroid out and have a pathologist look at it.” If the pathology indicates cancer, the surgeon will then return to the OR to remove the remaining thyroid.
In the absence of cancer, when only one lobe of the thyroid is affected, surgeons can remove only the involved lobe. Patients can do quite well with one functioning lobe, Dr. Quintana says, “particularly because the residual lobe preserves parathyroid function, and the native gland is still potentially putting out enough hormone to sustain a normal level.”
The Connection with Breast Cancer.
A recent study suggested that women being treated for breast cancer have a higher than normal risk of developing thyroid cancer. “It’s vitally important for primary care physicians and anyone treating women to understand that connection,” Dr. Quintana says. “And women should not only be urged to have their screening mammograms regularly, but also to examine their necks for lumps that could indicate nodules.”
Final Thoughts.
The availability of ultrasound and other advanced diagnostic tools are largely responsible for the increase in the diagnosis of thyroid nodules and thyroid cancer. “It’s always been there; we’re just better able to recognize it,” Dr. Lieb says. “As an endocrinologist, I feel like a part of my job is to stay on top on developments in the management of all aspects of thyroid disease, because our primary care physician colleagues have more to do than ever. For those physicians, and for interested patients, Dr. Lieb and the other contributors to this article recommend these websites:
The American Thyroid Association
www.thyroid.org
Thyroid Cancer Survivors’ Association
www.thyca.org
American Association of Endocrine Surgeons
www.endocrinesurgery.org
