Clinical trial NCT00565864: Neurocognitive and Metabolic Effects of Mild Hypothyroidism
Official title: Neurocognitive and Metabolic Effects of Mild Hypothyroidism
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE4
Conditions: Hypothyroidism
Keywords: Hypothyroidism
Cognition
Metabolism
Lead sponsor: Oregon Health and Science University
Sponsor class: OTHER
First posted: 2007-11-30
Enrollment: 173
Sex: ALL
Minimum age (years): 20
Maximum age (years): 75
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief 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.

Detailed description: Thyroid hormone is essential for neurocognitive and metabolic function, and patients with overt thyroid dysfunction have well-described alterations in mood, cognition, energy expenditure, and body composition. However, it is not clear that patients with more mild degrees of thyroid dysfunction have clinically significant alterations in these parameters.

In addition, recent data suggest that variations in thyroid function within the laboratory reference range may also affect these parameters.

Patients with hypothyroidism are routinely treated with levothyroxine (L-T4) as replacement therapy. Physicians monitor the L-T4 dose by measuring serum thyroid stimulating hormone (TSH) levels, with the goal of a normal level. However, many patients with normal TSH levels continue to report symptoms, primarily in neurocognitive and metabolic areas. For this reason, patients with hypothyroidism often request higher L-T4 doses, but the clinical consequences of this are unknown.

In the present study, otherwise healthy subjects with treated hypothyroidism and normal TSH levels, ages 20-75 years, will be enrolled in a 7-11 month study. At baseline, the following tests will be performed to measure health status, psychological symptoms, mood, memory, body composition, and energy expenditure: the Short Form Health Survey-36 (SF-36), Profile of Mood States (POMS), Affective Lability Scale (ALS), Letter Cancellation Test (LCT), Trail Making Test, Iowa Gambling Task (IGT), N-Back Test, Subject-Ordered Pointing, Paragraph Recall, Pursuit Rotor, Motor Sequence Learning Test, resting energy expenditure (REE) and thermic effect of food (TEF) by indirect calorimetry, total energy expenditure (TEE) by doubly labelled water, physical activity energy expenditure (PAEE) by accelerometry, diet intake by 24-hour diet recalls, and body composition by dual energy x-ray absorptiometry (DEXA). Following these baseline measurements, subjects will receive either their usual doses of L-T4, 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 L-T4 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.

Eligibility criteria: Inclusion Criteria:

* Ages 20-75
* Primary hypothyroidism on stable dose of L-T4 for \> 3 months
* Documented elevated TSH off L-T4
* Normal TSH level on usual dose of L-T4
* No acute or chronic medical or psychiatric illnesses that affect thyroid function, mood or cognition
* No medication use that affects thyroid function, mood or cognition (oral contraceptives or estrogen therapy allowed)
* Normal score on screening Mini-Mental State Exam (MMSE) (to test for dementia)
* Normal vision by screening examination
* Normal hearing by screening examination
* Non smoker

Exclusion Criteria:

* Failure to meet any of the above inclusion criteria
* Inability to speak and comprehend English
* A history of coronary artery disease
* Screening hgb \<10
* Screening wbc \> 10,000
* Clinically significant abnormalities on screening metabolic set
* Screening LDL cholesterol \> 160
* Screening triglyceride \> 300
* Significant abnormalities on screening ECG
* Pregnancy or intent to become pregnant in next 6 months
* Present or recent use of medications that affect thyroid hormone levels or interfere with thyroid hormone effects, including beta-blockers, lithium, glucocorticoids, or iodine containing agents
* MMSE score \< 26

Primary outcomes:
measure: Executive Function
timeFrame: 24 weeks
measure: Resting Energy Expenditure
timeFrame: 24 weeks
Secondary outcomes:
Other outcomes:
measure: Quality of Life by SF-36 Survey
timeFrame: 24 weeks
measure: Mood
timeFrame: 24 weeks
measure: Working Memory
timeFrame: 24 weeks
measure: Declarative Memory
timeFrame: 24 weeks
measure: Motor Learning
timeFrame: 24 weeks
measure: Total Energy Expenditure
timeFrame: 24 weeks
measure: Thermic Effect of Food
timeFrame: 24 weeks
measure: Physical Activity Energy Expenditure
timeFrame: 24 weeks
measure: Daily Energy Intake
timeFrame: 24 weeks
measure: Body Mass Index
timeFrame: 24 weeks
measure: Lean Body Mass
timeFrame: 24 weeks
measure: % Fat Mass
timeFrame: 24 weeks
Locations:
city: Portland
country: United States
facility: Oregon Health and Science University
state: Oregon
Study officials:
affiliation: Oregon Health and Science University
name: Mary Samuels, MD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Samuels MH, Kolobova I, Niederhausen M, Purnell JQ, Schuff KG. Effects of Altering Levothyroxine Dose on Energy Expenditure and Body Composition in Subjects Treated With LT4. J Clin Endocrinol Metab. 2018 Nov 1;103(11):4163-4175. doi: 10.1210/jc.2018-01203.
citation: Samuels MH, Kolobova I, Niederhausen M, Janowsky JS, Schuff KG. Effects of Altering Levothyroxine (L-T4) Doses on Quality of Life, Mood, and Cognition in L-T4 Treated Subjects. J Clin Endocrinol Metab. 2018 May 1;103(5):1997-2008. doi: 10.1210/jc.2017-02668.
citation: Samuels MH, Kolobova I, Antosik M, Niederhausen M, Purnell JQ, Schuff KG. Thyroid Function Variation in the Normal Range, Energy Expenditure, and Body Composition in L-T4-Treated Subjects. J Clin Endocrinol Metab. 2017 Jul 1;102(7):2533-2542. doi: 10.1210/jc.2017-00224.
citation: Samuels MH, Kolobova I, Smeraglio A, Niederhausen M, Janowsky JS, Schuff KG. Effect of Thyroid Function Variations Within the Laboratory Reference Range on Health Status, Mood, and Cognition in Levothyroxine-Treated Subjects. Thyroid. 2016 Sep;26(9):1173-84. doi: 10.1089/thy.2016.0141. Epub 2016 Jul 25.
citation: Samuels MH, Kolobova I, Smeraglio A, Peters D, Purnell JQ, Schuff KG. Effects of Levothyroxine Replacement or Suppressive Therapy on Energy Expenditure and Body Composition. Thyroid. 2016 Mar;26(3):347-55. doi: 10.1089/thy.2015.0345. Epub 2016 Feb 3.
citation: Samuels MH, Kolobova I, Smeraglio A, Peters D, Janowsky JS, Schuff KG. The effects of levothyroxine replacement or suppressive therapy on health status, mood, and cognition. J Clin Endocrinol Metab. 2014 Mar;99(3):843-51. doi: 10.1210/jc.2013-3686. Epub 2014 Jan 13.