ESTES PARK, COLO. – The latest major guidelines on management of hypothyroidism create a new, looser treatment target for older patients.
“This is a departure from the message we’ve given many times in the past. Elderly people seem to tolerate slight degrees of hypothyroidism and may actually benefit from it,” Dr. Michael T. McDermott said at a conference on internal medicine sponsored by the University of Colorado.
The American Thyroid Association guidelines issued late last year (Thyroid. 2014 Dec;24:1670-75) raise the target serum TSH to 4-6 mIU/L in hypothyroid individuals age 70 or older. The target serum TSH in nonelderly, nonpregnant patients remains unchanged at 0.5-4.5 mIU/L, noted Dr. McDermott, professor of medicine and director of endocrinology and diabetes practice at the University of Colorado Hospital, Aurora.
“The slightly higher TSH treatment target in elderly patients is very heavily evidence-based. Studies showed that people over age 70 often did worse if their TSH was maintained in the low end of the normal range, and that people whose TSH was maintained up to about 6 mIU/L didn’t seem to have any adverse effects from that. It’s kind of a moving target: we’ll probably see the data reevaluated over time. But I think it’s clear that normal elderly people have a normal TSH that’s slightly higher,” according to the endocrinologist.
The starting dose of levothyroxine (LT4) in older patients is 25-50 mcg/day. The TSH level should be rechecked after 6 weeks in patients with overt hypothyroidism and 6-10 weeks in those with subclinical hypothyroidism, with LT4 then being titrated in the elderly until it’s in the 4-6 mIU/L range.
Speaking of subclinical hypothyroidism, which is defined by an elevated TSH but a normal free T4 level, four studies now show the same thing: While subclinical hypothyroidism is independently associated with increased cardiovascular mortality in patients under age 65, it does not carry any increased cardiovascular mortality risk in older individuals. The first of these studies, a meta-analysis of 15 clinical trials totalling 2,531 subclinically hypothyroid patients and more than 26,000 controls, found a 37% increase in cardiovascular mortality in patients younger than 65 with subclinical hypothyroidism, but no increase in older people with the disorder (J Clin Endocrinol Metab. 2008 Aug;93:2998-3007).
“We don’t know why that is, but it’s the reason the recommended TSH range when treating people for subclinical or overt hypothyroidism has now changed in people over age 70,” Dr. McDermott explained.
The consensus recommendations of the American Thyroid Association and the American Association of Clinical Endocrinologists advise treatment of subclinical hypothyroidism involving a TSH level greater than 10.0 mIU/L. In patients with lesser elevations of TSH, however, clinical judgment is critical in deciding whether to treat or monitor.
“If the person has symptoms, treatment is very reasonable. You should know, however, that one-third of people who have a TSH of 4.5-10.0 mIU/L will have a normal TSH 1 year later if you don’t treat them. So if they’re not symptomatic you may usually monitor these patients,” he said.
While LT4 remains the treatment of choice for hypothyroidism, 16% of patients have persistent symptoms despite optimal LT4 therapy. They appear to benefit from a combination of LT4 and liothyronine (LT3) given in a 10:1 ratio. Because LT3 lasts for only about 8 hours, it’s best administered twice daily. Thyroid tests should be obtained before the medication is taken because triiodothyronine (T3) levels rise abruptly in response to a dose.
Dr. McDermott reported having no financial conflicts of interest.