Neurocognitive and Metabolic Effects of Mild Hypothyroidism
Status:
Completed
Trial end date:
2013-08-01
Target enrollment:
Participant gender:
Summary
Patients with hypothyroidism are routinely treated with thyroid hormone (l-thyroxine) for
replacement therapy. Physicians monitor the thyroid hormone dose by measuring a thyroid
stimulating hormone (TSH) level in the blood, with the goal of a normal level. However,
recent data suggest that the "normal" TSH range is too broad, and that patients may still
have symptoms if their TSH levels are at the top or bottom part of the normal range.
To study this issue, it is useful to address issues such as general health status,
psychological symptoms, mood, memory, and metabolic status, since thyroid hormone has major
effects on the brain and metabolism, and since patients with treated hypothyroidism often
have symptoms related to these areas.
In the present study, otherwise healthy subjects with treated hypothyroidism, ages 20-75
years, will be enrolled in a 7-11month study. At baseline, they will have tests of health
status, psychological symptoms, mood, memory, body composition, and energy expenditure
performed. Following these baseline measurements, subjects will receive either their usual
doses of l-thyroxine, or a slightly higher or lower dose. The doses will be chosen to try to
achieve either a low-normal TSH level, a high-normal TSH level, or a mildly elevated TSH
level. Which target TSH the patient is assigned will be determined randomly, and neither the
subject nor the study contacts will know which dose the patient is receiving. Subjects will
be seen every 6 weeks during the study for brief visits to make sure they are not having any
side effects, and to adjust the l-thyroxine doses if the TSH has not yet reached the target
range. At the 24-week visit (end of study), the subjects will undergo the same tests that
they had on the baseline visit.
Results from the study will be examined to see if minor changes in TSH or other thyroid
hormone levels cause changes in any of the outcomes, and if the degree of TSH change
correlates with the degree of outcome changes. These results may help physicians caring for
patients with thyroid disease better determine the optimal dose of thyroid hormone for each
patient.