Functional correlates of TSH, fT3 and fT4 in Alzheimer disease: a F-18 FDG PET/CT study

Abstract

The present study was aimed to investigate the relationships between thyroid stimulating hormone (TSH), freeT3 (fT3) and freeT4 (fT4) and brain glucose consumption as detectable by means of 2-deoxy-2-(F-18) fluoro-D-glucose (F-18 FDG) Positron Emission Tomography/Computed Tomography (PET/CT) in a selected population with Alzheimer disease (AD). We evaluated 87 subjects (37 males and 50 females, mean age 70 (±6) years old) with AD. All of them were subjected to TSH, fT3 and fT4 assay and to cerebrospinal fluid amyloid (Aβ1-42) and tau [phosphorylated-tau (p-tau) and total-tau (t-tau)] assay prior PET/CT examination. Values for TSH, fT3 and fT4 were in the normal range. The relationships were evaluated by means of statistical parametric mapping (SPM8) using age, sex, MMSE, scholarship and CSF values of amyloid and tau as covariates. We found a significant positive correlation between TSH values and cortical glucose consumption in a wide portion of the anterior cingulate cortex bilaterally (BA32) and left frontal lobe (BA25) (p FWE-corr <0.001; p FDRcorr <0.000; cluster extent 66950). No significant relationships were found between cortical F-18 FDG uptake and T3 and T4 serum levels. The results of our study suggest that a cortical dysfunction in anterior cingulate and frontal lobes may affect serum values of TSH in AD patients.

Association of serum thyroid hormone levels with positron emission tomography imaging in non‐demented older adults

“…The serum TSH levels were positively associated with global glucose metabolism and glucose metabolism in the frontal lobe. To our knowledge, only one FDG‐PET study showed a positive correlation between serum TSH levels within the reference range and glucose metabolism in the frontal lobe in AD patients 17 . This finding is consistent with our results regardless of differences in the clinical characteristics of participants.…”

“…To our knowledge, only one study has reported that serum TSH levels within the reference range were positively correlated with frontal glucose metabolism in AD patients. 17 Therefore, the present study aimed to determine whether variations in serum thyroid hormone levels within the reference range are associated with both Aβ deposition and cortical glucose metabolism in older adults without dementia.…”

Association between thyroid hormone levels and frailty in an older inpatient cohort: a cross-sectional study

“…However, in other studies, clinical events were reported to be significantly associated with TSH, but not FT4. For example, metformin treatment significantly lowered serum TSH, but did not change serum FT4 (33), and Chiaravalloti et al (34) found a significant positive correlation between serum TSH and cortical F-18 FDG uptake in patients with Alzheimer's disease, but no significant relationship between cortical F-18 FDG uptake and serum FT4. As serum TSH tends to become higher with increasing age (35), we suppose that pituitary sensitivity to FT4 is enhanced in aging persons.…”

The relationship between thyroid function and cerebral blood flow in mild cognitive impairment and Alzheimer’s disease

“…Kimura et al identified a significant inverse correlation between TSH levels within the normal range and rCBF in the right middle and inferior temporal regions in AD patients [4]. Meanwhile, Chiaravalloti et al demonstrated a positive correlation between TSH levels within the normal range and cortical glucose consumption in the bilateral anterior cingulate cortices and left frontal lobe [5]. Furthermore, Haji et al reported significant decreases in rCBF localized in the temporal lobe and thalamus in AD patients with SCH [6].…”