Clinical Thyroidology® for the Public
Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID FUNCTION
Changes in thyroid function predict brain decline in the very old
BACKGROUND
Changes in thyroid function are common in older adults, and both overactive thyroid (hyperthyroidism) and underactive thyroid (hypothyroidism) have been associated with brain impairment and dementia. However, the relationship between subclinical thyroid disease (i.e., a mild form of thyroid disease where the only abnormal hormone level is a thyroid stimulating hormone or TSH) and brain function remains unclear. Some prior studies have suggested that the risk of dementia in adults aged 65 years and older increased with low TSH, while mildly high TSH has been shown to be associated with preserved brain function and longevity. Most of these prior studies included very small numbers of the oldest old, i.e., adults aged 85 years and older. This study aimed to examine the relationship between changes in thyroid function and brain function in adults aged 85 years and older.
THE FULL ARTICLE TITLE
Gan EH et al. Changes in serum thyroid function predict cognitive decline in the very old: Longitudinal findings from the Newcastle 85+ study. Thyroid. Epub 2021 Jun 2. PMID: 34074153.
SUMMARY OF THE STUDY
This study included 642 participants from the Newcastle 85+ Study. Participants were 85 years and older from Newcastle and North Tyneside in the United Kingdom, had TSH levels between 0.1 and 10 mIU/L and normal free T4 and free T3 levels at baseline. Data collected included questionnaires, measurements such as height and weight, physical and brain testing, and fasting blood samples at baseline, 3 and 5 years. A change of 0.1 mIU/L in the TSH was defined as a change in thyroid function status. Patients taking medications that interfere with thyroid function tests, such as levothyroxine and amiodarone, and patients with overt hypothyroidism or hyperthyroidism were excluded.
Brain function was evaluated using the Mini-Mental State Examination (MMSE), with higher score denoting higher brain performance, and the Cognitive Drug Research (CDR) computerized assessment system which assesses memory and attention.
Overall, 58.1% of participants were women and 54.2% of them were alive for their 3-year follow-up. A total of 63.5% of participants had decreasing TSH over time. Patients with the lowest TSH at baseline had the highest rates of brain impairment and decreasing TSH over time was associated with decreasing scores on MMSE following 3 and 5 years. Lower free T3 levels at baseline were also associated with development of brain impairment by 5 years. Changes in free T4 and free T3 over time were not associated with changes in brain function.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Overall, 58.1% of participants were women and 54.2% of them were alive for their 3-year follow-up. A total of 63.5% of participants had decreasing TSH over time. Patients with the lowest TSH at baseline had the highest rates of brain impairment and decreasing TSH over time was associated with decreasing scores on MMSE following 3 and 5 years. Lower free T3 levels at baseline were also associated with development of brain impairment by 5 years. Changes in free T4 and free T3 over time were not associated with changes in brain function.
— Maria Papaleontiou, MD
ATA THYROID BROCHURE LINKS
Older Patients and Thyroid Disease: https://www.thyroid.org/thyroid-disease-older-patient/
Thyroid Function Tests: https://www.thyroid.org/thyroid-function-tests/
ABBREVIATIONS & DEFINITIONS
TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also the best screening test to determine if the thyroid is functioning normally.
Hypothyroidism: a condition where the thyroid gland is underactive and doesn’t produce enough thyroid hormone. Treatment requires taking thyroid hormone pills.
Subclinical Hypothyroidism: a mild form of hypothyroidism where the only abnormal hormone level is an increased TSH. There is controversy as to whether this should be treated or not.
Overt Hypothyroidism: clear hypothyroidism an increased TSH and a decreased T4 level. All patients with overt hypothyroidism are usually treated with thyroid hormone pills.
Hyperthyroidism: a condition where the thyroid gland is overactive and produces too much thyroid hormone. Hyperthyroidism may be treated with antithyroid meds (Methimazole, Propylthiouracil), radioactive iodine or surgery.
Subclinical Hyperthyroidism: a mild form of hyperthyroidism where the only abnormal hormone level is a decreased TSH.
Cognition: the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses.
Thyroxine (T4): the major hormone produced by the thyroid gland. T4 gets converted to the active hormone T3 in various tissues in the body.
Triiodothyronine (T3): the active thyroid hormone, usually produced from thyroxine.
Mini-Mental State Examination (MMSE): is a widely used test of cognitive function among older adults; it includes tests of orientation, attention, memory, language and visual-spatial skills. It is scored from 0 to 30 possible points, with higher score indicating higher cognitive performance. A normal cognitive status is defined as an MMSE score of 26 points or higher.
Cognitive Drug Research (CDR): computerized assessment system: Assesses episodic memory and attention.
Hypothalamus: this is an area of the brain that produces hormones that control body temperature, hunger, mood, and release of hormones from many glands, especially the pituitary gland.
Pituitary gland: this endocrine gland sits at the base of the brain and secretes hormones that control thyroid and adrenal function, growth and reproduction. The pituitary gland secretes TSH to control thyroid function.
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