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Lifetime thyroid hormone replacement is likely: subclinical hypothyroidism.

PALM BEACH, FLA. -- Women with subclinical hypothyroidism should receive thyroid hormone replacement therapy for life, according to a study presented at the annual meeting of the American Thyroid Association.

Subclinical hypothyroidism can have detrimental effects on the heart and lipid levels, recent studies have shown (Ann. Pharmacother. 37[5]:725-30, 2003; Thyroid 12[5]:421-25, 2002). Therefore, replacement therapy with synthetic thyroid hormone (levothyroxine) may be indicated for its cardioprotective effects.

To determine the appropriate duration of therapy, Dr. Irma Gazeroglu and her colleagues at the University of Miami assessed 30 women with subclinical hypothyroidism.

Levothyroxine therapy was started when thyroid-stimulating hormone levels were between 4 [micro]IU/mL and 11 [micro]IU/mL on two to three consecutive assessments. Follow-up between 2 and 5 years after initiation of levothyroxine therapy (mean dose 0.98 [micro]g/kg) was completed in 22 participants, and they were analyzed further.

The women were grouped according to their last levothyroxine dose requirement. There were nine women whose requirement for levothyroxine increased over time, to a mean dose of 1.65 [micro]g/kg; this signifies that their thyroid function was deteriorating, Dr. Gazeroglu said. A second group of 13 women required the same mean dose (0.99 [micro]g/kg) to maintain their hormone levels. There were no significant differences between the two groups in terms of mean age or thyroid antibody status.

At 3 weeks prior to the follow-up visit, levothyroxine therapy was discontinued in the stable-dose group. "'We took these women off to see if the benefit would be reversed," said Dr. Gazeroglu, an endocrinology fellow in the department of medicine at the university.

The thyroid-stimulating hormone level increased to pretreatment levels in nine women and increased in two women to 12.3 [micro]IU/mL and 15.2 [micro]IU/mL. Data were unavailable for one participant. "Only one still had normal TSH levels," Dr. Gazeroglu said.

The implication is that once initiated, replacement therapy for subclinical hypothyroidism should be prescribed permanently, she said.
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Title Annotation:Clinical Rounds
Author:McNamara, Damian
Publication:OB GYN News
Date:Nov 15, 2003
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