What is the thyroid gland?

The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The thyroid’s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroid hormone helps the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.

Definition: What do the following patients over the age of 60 years have in common?

1. A 72 year old woman with “fluttering of the heart” and vague chest discomfort on climbing stairs
2. An 80 year old man with severe constipation who falls asleep often
3. A 65 year old woman who has lost strength in her legs, causing difficulty in climbing stairs;she has recently lost 15 lbs in spite of a very good appetite
4. A 75 year old woman who has developed difficulty swallowing and a dry cough, accompanied by hoarseness, weight gain, and dry, itchy skin
5. A 78 year old man with hearing loss
6. An 84 year old woman in whom a hand tremor has caused her to give up favorite activities. She is so depressed that she will not eat, and she has lost 12 lbs in the last 4 months.

All of these patients have abnormal function of their thyroid glands. Patients 1, 3 and 6 have hyperthyroidism, that is, excessive production of thyroid hormone by their thyroid glands. Patients 2, 4 and 5 have hypothyroidism, or reduced production of thyroid hormone. While some of the symptoms of hyperthyroidism and hypothyroidism are similar to those in younger patients, it is not uncommon for both hyperthyroidism and hypothyroidism to be manifest in subtle ways in older patients, often masquerading as diseases of the bowel or heart or a disorder of the nervous system. An important clue to the presence of thyroid disease in an elderly patient is a history of thyroid disease in another close family member such as a brother, sister or child of the patient.

Hyperthyroidism in the older patient

As in all hyperthyroid patients, if there is too much thyroid hormone, every function of the body tends to speed up (see Hyperthyroidism brochure). However, while the younger patient often has multiple symptoms related to the overactive thyroid, the elderly patient may only have one or two symptoms. For example, patient number 1, above, experienced only a sensation of her heart fluttering, and some chest discomfort on climbing stairs. Other patients may also have few symptoms, such as patient number 6, whose main symptoms are depression and tremor. Such a patient may withdraw from interactions with friends and family.

Treatment of the older patient with hyperthyroidism

As with younger patients, treatment of hyperthyroidism in the older patient includes antithyroid drugs and radioactive iodine (see Hyperthyroidism brochure). Surgery is rarely recommended due to increased operative risks in the older patient. While Graves’ disease is still a common cause of hyperthyroidism, toxic nodular goiter is seen more frequently in the older patient. During therapy, the effects of change in thyroid function on other body systems must be closely monitored, due to an increased likelihood of co-existing cardiac, central nervous system and thyroid disease in older patients. Most often, thyroid function is brought under control first with antithyroid drugs (propylthiouracil or methimazole (Tapazole®)) before definitive treatment with radioactive iodine.

During the initial phase of treatment, doctors will observe cardiac function closely due to the effect of changing thyroid hormone levels on the heart. Symptoms of hyperthyroidism may be brought under control with adjunctive medications, such as beta-adrenergic blockers (propranolol [Inderal®], metoprolol [Lopressor ®]), which are often given to slow a rapid heart rate, although they must be given with caution in the patient with co-existing congestive heart failure and the dose should be reduced once thyroid function is controlled in the normal range. Symptoms and signs of angina pectoris and heart failure must be treated in tandem with the treatment to bring thyroid function under control.

Once thyroid function is maintained in the normal range with oral medication, the doctor and patient can make a decision on definitive treatment with radioactive iodine together. There is some controversy about what the normal level of TSH is for elderly patients. In general, an attempt is made to render thyroid function either normal or low in an elderly patient treated with radioactive iodine. Treatment of an underactive thyroid condition (hypothyroidism) is usually more straightforward than the problem of recurrent hyperthyroidism in the older patient, because of the effect hyperthyroidism can have on the heart, as indicated above. A frequent clinical concern is the treatment of patients with normal T4 and T3 with suppressed TSH. An isolated low TSH is particularly common in older patients. Most clinicians will follow these patients, without treatment unless they are symptomatic.

Hypothyroidism in the older patient

Hypothyroidism is very common in patients over 60 years of age and steadily increases with age (see Hypothyroidism brochure). Up to 1 in 4 patients in nursing homes may have undiagnosed hypothyroidism. Unlike symptoms of hyperthyroidism, the symptoms of hypothyroidism are very non-specific in all patients, even more so in the older patient. As with hyperthyroidism, the frequency of multiple symptoms decreases in the older patient. For example, memory loss or a decrease in cognitive functioning, often attributed to advancing age, may be the only symptoms of hypothyroidism present. Symptoms and signs of hypothyroidism may include weight gain, sleepiness, dry skin, and constipation, but lack of these symptoms does not rule out the diagnosis. To make this diagnosis in the elderly patient, a doctor often needs a high index of suspicion. Clues to the possibility of hypothyroidism include a positive family history of thyroid disease, past treatment for hyperthyroidism, or a history of extensive surgery and/or radiotherapy to the neck.

A decision to treat the patient with a new diagnosis of hypothyroidism will rest on several factors, including whether the patient is symptomatic from hypothyroidism, or just has an elevated thyroid-stimulating hormone (TSH) level. In the case of the latter finding, many doctors will repeat the test in 3-4 months and elect to begin thyroid hormone replacement when the TSH level stays above the normal range. The presence or absence, and severity, of thyroid-related symptoms and co-existing diseases such as coronary artery disease or heart failure will determine the dose of thyroid hormone replacement that is given.

Treatment of the older patient with hypothyroidism

As with the younger patient, pure synthetic thyroxine (L-T4), taken once daily by mouth, fully replaces the function of the thyroid gland and successfully treats the symptoms of hypothyroidism in most patients (see Thyroid Hormone Treatment brochure). In particular, treatment of the older hypothyroid patient must take into account that full thyroid hormone replacement need not take place rapidly, and in fact may put stress on the heart and central nervous system if accomplished too quickly. Rather, hormone treatment is usually begun slowly with a partial daily dose, in order to allow the heart and central nervous system to adjust to increasing levels of thyroid hormone. The patient and family members must be aware of a possible increase in angina, shortness of breath, confusion and change in sleep habits, and notify the prescribing physician if these occur.

Treatment may therefore begin with L-T4 in a dose of 25 to 50 micrograms daily, and the dose increased in steps every 4-6 weeks until the laboratory tests show a gradual return of blood thyroid hormone and thyroid-stimulating hormone (TSH) levels to the normal range. Older patients with no evidence of heart disease, stroke or dementia may be started on larger doses (for example, half of the anticipated full replacement dose) and proceed to full hormone replacement more quickly. In patients who experience increased angina pectoris, symptoms of congestive heart failure, or mental changes such as confusion will need to have their dose of L-T4 decreased, then more gradually increased over several months’ time.

Summary

Thyroid disorders have no age limits; indeed, hypothyroidism is clearly more common in older than in younger adults. Despite the increased frequency of thyroid problems in older individuals, physicians need a high index of suspicion to make the diagnosis since thyroid disorders often manifest as a disorder of another system in the body. Older patients with thyroid disorders require special attention to gradual and careful treatment, and, as always, require lifelong follow-up.

Further Information

Further details on this and other thyroid-related topics are available in the patient information section on the American Thyroid Association^® website at www.thyroid.org.

Thyroid Disease in the Older Patient Brochure for Saving and Printing (PDF File, 443KB)

Thyroid Disease in the Older Patient Brochure for Saving and Printing (PDF File, 172KB)

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This problem has been found to be especially important in post menopausal women and older men (3) who are at increased risk for fractures from worsening osteoporosis when overtreated with thyroid hormones (4). Thyroid hormones have a direct action on bone cells leading to bone loss (5) . TSH, which may play a role in protecting bone (6), is also low in overtreated patients. On the other hand, patients with hypothyroidism treated with doses of thyroxine that keep TSH within the normal range, do not appear to be at increased risk of fracture (4,7). For this reason, regular monitoring of thyroid replacement therapy every 6-12 months once stabilized, using serum TSH as a gauge, is the current standard of care (1).

This issue is again emphasized by a new study from Toronto, Canada published in the British Medical Journal examining the health records of 213,511 patients over the age of 70 years who were taking thyroxine over a 3.8 year period (8). 10.4% had a fracture during this time and 88% of the fractures were in women. The risk of fracture was almost double for those currently taking thyroid hormone as compared to those who only used it years ago. Those patients taking higher doses of thyroxine were more likely to have had a fracture than those taking lower doses. Unfortunately serum TSH data were not available so it is not certain which patients were properly treated, but it is plausible that many patients were overtreated, especially those who received higher doses. This supports the importance of avoiding overtreatment with thyroxine by adjusting the dose carefully through TSH monitoring.

Age itself is a risk factor for osteoporosis and fracture (9). Additionally, older patients need less thyroxine to maintain a euthyroid state (10,11). Failure to recognize the relationship of age and thyroxine requirements will lead to over dosage if the dose of thyroxine is not titrated down as patients age. Unnecessary treatment of elderly patients adds to this danger. The diagnosis of thyroid failure in the elderly needs to be carefully evaluated with the knowledge that the upper normal value for TSH in people over 80 yrs is ~7.5 uU/ml, compared to 4.0 uU/ml in young adults (12). Therefore careful selection of which elderly patients should be treated with thyroxine is critical. Thyroid hormone overtreatment of elderly patients is an avoidable problem.

Individuals vary in their absorption of thyroxine, sometimes because of use of interfering medications, higher thyroxine doses may be required for some patients to achieve normal TSH levels. This should not contribute to bone loss as long as overtreatment is avoided. Further, some patients with thyroid cancer need to have a lower TSH levels to prevent cancer recurrence (13). In these selected patients the risk of bone loss is outweighed by beneficial effects on control of the cancer. Hence, it is important is to adjust the dose of thyroxine to achieve TSH levels that are appropriate for each individual patient.

References:

1.  Singer PA, Cooper DS, Levy EG, Ladenson PW, Braverman LE, Daniels G, Greenspan FS, McDougall IR, Nikolai TF 1995 Treatment guidelines for patients with hyperthyroidism and hypothyroidism. Standards of Care Committee, American Thyroid Association. J A M A 273:808-812
2.  Canaris GJ, Manowitz NR, Mayor G, Ridgway EC 2000 The Colorado thyroid disease prevalence study. Arch Int Med 160:526-534
3.  Sheppard MC, Holder R, Franklyn JA 2002 Levothyroxine treatment and occurrence of fracture of the hip. Arch Int Med 162:338-343
4.  Bauer DC, Ettinger B, Nevitt MC, Stone KL 2001 Risk for fracture in women with low serum levels of thyroid-stimulating hormone. Ann Int Med 134:561-568
5.  Murphy E, Williams GR 2004 The thyroid and the skeleton. Clinical Endocrinology 61:285-298
6.  Imam A, Iqbal J, Blair HC, Davies TF, Huang CL, Zallone A, Zaidi M, Sun L 2009 Role of the pituitary-bone axis in skeletal pathophysiology. Curr Op Endocrinol Diab 16:423-429
7.  Flynn RW, Bonellie SR, Jung RT, MacDonald TM, Morris AD, Leese GP 2010 Serum thyroid-stimulating hormone concentration and morbidity from cardiovascular disease and fractures in patients on long-term thyroxine therapy. J Clin Endocrinol Metab 95:186-193
8.  Turner MR, Camacho X, Fischer HD, Austin PC, Anderson GM, Rochon PA, Lipscombe LL 2011 Levothyroxine dose and risk of fractures in older adults: nested case-control study. BMJ 342:d2238
9.  Syed FA, Ng AC 2010 The pathophysiology of the aging skeleton. Curr Osteoporos Rep 8:235-240
10.  Kabadi UM 1997 Influence of age on optimal daily levothyroxine dosage in patients with primary hypothyroidism grouped according to etiology. Southern Medical Journal 90:920-924
11.  Sawin CT, Herman T, Molitch ME, London MH, Kramer SM 1983 Aging and the thyroid. Decreased requirement for thyroid hormone in older hypothyroid patients. Am J Med 75:206-209
12. Boucai L, Hollowell JG, Surks MI 2011 An approach for development of age-, gender-, and ethnicity-specific thyrotropin reference limits. Thyroid 21:5-11
13. Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri EL, McIver B, Pacini F, Schlumberger M, Sherman SI, Steward DL, Tuttle RM 2009 Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 19:1167-1214

The American Thyroid Association (ATA) is the leading worldwide organization dedicated to the advancement, understanding, prevention, diagnosis and treatment of thyroid disorders and thyroid cancer. ATA is an international individual membership organization with over 1,400 members from 43 countries around the world. Celebrating its 88th anniversary, ATA delivers its mission through several key endeavors: the publication of highly regarded monthly journals, THYROID, Clinical Thyroidology and Clinical Thyroidology for Patients; annual scientific meetings; biennial clinical and research symposia; research grant programs for young investigators, support of online professional, public and patient educational programs; and the development of guidelines for clinical management of thyroid disease.

More information about ATA is found at www.thyroid.org

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