Cerebral accumulation of Tc-99m ethyl cysteinate dimer (ECD) in severe, transient hypothyroidism

Abnormal Brain Glucose Metabolism in Papillary Thyroid Cancer Patients 4 Weeks After Withdrawal of Levothyroxine: A Cross-Sectional Study Using 18F-FDG PET/CT

Background

There is no doubt that thyroid dysfunction is associated with psychiatric disorders. A large amount of thyroid carcinoma patients displayed mood disorders after the withdrawal of levothyroxine (LT4). However, it is unclear whether the disorders are related to the transient withdrawal of LT4, and if yes, what the possible underlying mechanism is. This study aims to investigate the abnormal regional cerebral glucose metabolism (rCMRglu) in a group of papillary thyroid cancer (PTC) patients without LT4 for 4 weeks and prove the relationship between the abnormal rCMRglu with depression and anxiety.

Methods

Brain 18F-FDG PET/CT data of 38 consecutive PTC patients with high/intermediate-risk from June 2016 to December 2017 have been analyzed. Of the 38 patients, 23 are in the LT4 withdrawal group (WG) and 15 in the LT4 replacement group (RG). These patients were also evaluated for depressive and anxiety symptoms within 24 h after the scans based on the Hamilton Depression Rating Scale (17 items, HRDS-17) and the Hamilton Anxiety Rating Scale (HAMA) respectively.

Results

Thirty-eight patients (12 men, 26 women; age range, 25-69 years; mean age, 45.8 years) were selected in the study. Compared with the RG, patients in WG showed depression and anxiety with higher total scores of HRDS-17 and HAMA (14.7 ± 5.8 vs 3.8 ± 5.5, t = -5.74, p = 0.00; 9.3 ± 4.3 vs 2.7 ± 4.1, t = -4.74, p = 0.00, respectively). In the brain glucose metabolism analysis, the WG patients showed lower rCMRglu in Occipital_Mid_R and Postcentral_L. On the other hand, data illustrated significant rCMRglu increases in the Frontal_Sup_Orb_L. Compared with the healthy group (HG), the rCMRglu of the Postcentral_L and Precuneus_L showed hypoactivity, but the Hippocampus_R and the Temporal_Inf_L showed hyperactivity. This analysis yielded a significant correlation between abnormal rCMRglu with the free thyroxine level, the serum thyroid-stimulating hormone level, HRDS-17, and HAMA scores.

Conclusions

The findings showed that more PTC patients exhibited depression and anxiety after LT4 withdrawal for 4 weeks. More attention should be paid to these hypothyroid patients while they were in the hospital. Such a short-term LT4 withdrawal also likely induced abnormal rCMRglu. Our study attempts to explain the possible mechanism of mood disorders related to transient hypothyroidism.

Brain GABA+ changes in primary hypothyroidism patients before and after levothyroxine treatment: A longitudinal magnetic resonance spectroscopy study

OBJECTIVE

Increasing evidence indicates the involvement of the GABAergic system in the pathophysiology of hypothyroidism. We aimed to investigate longitudinal changes of brain GABA in primary hypothyroidism before and after levothyroxine (L-T4) treatment.

MATERIAL AND METHODS

In 18 patients with hypothyroidism, we used the MEGA-PRESS (Mescher-Garwood point-resolved spectroscopy) editing sequence to measure brain GABA levels from medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) at baseline and after 6-months of L-T4 treatment. Sex- and age-matched healthy controls (n = 18) were scanned at baseline. Thyroid function and neuropsychological tests were also performed.

RESULTS

GABA signals were successfully quantified from all participants with fitting errors lower than 15%. GABA signal was labeled as GABA+ due to contamination from co-edited macromoleculars and homocarnosine. In hypothyroid patients, mean GABA+ was significantly lower in the mPFC region compared with controls (p = 0.031), and the mPFC GABA+ measurements were significantly correlated with depressive symptoms and memory function (r = -0.558, p = 0.016; r = 0.522, p = 0.026, respectively). After adequate L-T4 treatment, the mPFC GABA+ in hypothyroid patients increased to normal level, along with relieved neuropsychological impairments.

CONCLUSION

The study suggested the decrease of GABA+ may be an important neurobiological factor in the pathophysiology of hypothyroidism. Treatment of L-T4 may reverse the abnormal GABA+ and hypothyroidism-induced neuropsychiatric impairments, indicating the action mode of L-T4 in adjunctive treatment of affective disorders.

Microstructural white matter abnormalities in hypothyroidism evaluation with diffusion tensor imaging tract-based spatial statistical analysis

PURPOSE

Hypothyroidism is presented in a wide range from neuropsychiatric problems including depression, memory and cognitive disorders to poor motor coordination. Against the background of morphologic, functional and molecular changes on the white and grey matter of the brain, we aimed to investigate the effects of hypothyroidism on white matter (WM) integrity using tract-based spatial statistics (TBSS).

METHODS

Eighteen patients with hyperthyroidism and 14 age-sex-matched healthy control subjects were included in this study. TBSS was used in the diffusion tensor imaging study for whole-brain voxel wise analysis of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) of WM.

RESULTS

When compared to the control group, the whole brain TBSS revealed extensive reductions of FA in the supratentorial WM including corticospinal tract, posterior limb of the internal capsule (PLIC), uncinate fasciculus, inferior longitudinal fasciculus (p < 0.005). The ROI analyses showed RD increment of superior longitudinal fasciculus, AD decrement of cingulum (CIN), external capsule, PLIC and corpus callosum (CC) in patients with hypothyroidism (p < 0.005). Autoimmune and non-autoimmune hypothyroidism patient subgroups showed a significant difference in terms of hippocampus FA, CIN MD, CC MD, CC AD, CIN RD, SLF RD, CC RD (p < 0.005). CIN FA values showed a negative correlation with the Beck Depression Inventory (p = 0.007, r = - 852).

CONCLUSIONS

These preliminary results of TBSS analyses represented FA and AD decrement, and RD increment in several WM tracts and indicates the demyelination process underlying pathophysiology of clinical aspects of hypothyroidism.

Cerebral glucose metabolism and Cerebral blood flow in thyroid dysfunction: An Activation Likelihood Estimation Meta-analysis

Thyroid dysfunction is frequently associated with functional disturbances of the brain. We performed a meta-analysis of previous positron emission tomography and single-photon emission computed tomography studies using a coordinate-based technique of activation-likelihood estimation (ALE) to investigate the potential background of neuropsychiatric complications in patients with hypo- and hyperthyroidism. We performed a systematic search of MEDLINE and EMBASE for English-language publications using the keywords of “positron emission tomography”, “single-photon emission computed tomography”, and “thyroid”. The software GingerALE ver 2.3.6 was used to transform all reported coordinates into stereotactic Montreal Neurological Institute space. A threshold of uncorrected p < 0.001 (minimum volume of 200 mm³) was applied to the resulting ALE map using cerebral metabolic rate of glucose (CMRglu), and cerebral blood flow (CBF). Six studies were eligible for inclusion in the study; 4 studies of cerebral metabolic rate of CMRglu, and 2 studies of CBF. In hypothyroidism, significant decreases in CMRglu were identified in 3 clusters including left anterior cingulate, right inferior occipital gyrus, and right cuneus. In hyperthyroidism, a significant decrease in CMRglu was identified in right superior frontal gyrus. In hypothyroidism, a significant decrease in CBF was observed in left postcentral gyrus. In conclusion, several brain regions showed altered CMRglu and CBF in patients with thyroid dysfunction compared with euthyroid controls. These findings might account for underlying mechanisms of thyroid hormones on psychological and physiological effects on brain.

Investigation of brain GABA+ in primary hypothyroidism using edited proton MR spectroscopy

OBJECTIVE

Evidence indicates that thyroid hormones have effects on the inhibitory GABAergic system. The aim of this study was to investigate whether brain GABA levels are altered in patients with hypothyroidism compared with healthy controls.

DESIGN/METHODS

Fifteen patients with primary hypothyroidism and 15 matched healthy controls underwent single-voxel MEGA-PRESS magnetic resonance spectroscopy at 3T, to quantify GABA levels in the median prefrontal cortex (mPFC) and posterior cingulate cortex (PCC). All participants underwent thyroid function test. Neuropsychological performances were evaluated by administration of the Montreal Cognitive Assessment (MoCA) and the 21-item Beck Depression Inventory-II (BDI-II).

RESULTS

The patients with hypothyroidism had significantly lower GABA+ levels in the mPFC compared with healthy controls (P = 0·016), whereas no significant difference (P = 0·214) was observed in the PCC. Exploratory analyses revealed that mPFC GABA+ levels were negatively correlated with the BDI-II scores in patient group (r = -0·60, P = 0·018). No correlations were found between GABA+ levels and TSH or fT3 or fT4 levels in either region (all P > 0·05).

CONCLUSION

This study suggests that alteration of GABAergic neurotransmission may play an important role in the pathophysiology of primary hypothyroidism, providing intriguing neurochemical clues to understand thyroid-brain interactions.

Differences in Brain Glucose Metabolism During Preparation for 131I Ablation in Thyroid Cancer Patients: Thyroid Hormone Withdrawal Versus Recombinant Human Thyrotropin

BACKGROUND

In preparation for ¹³¹I ablation, temporary withdrawal of thyroid hormone is commonly used in patients with thyroid cancer after total thyroidectomy. The current study aimed to investigate brain glucose metabolism and its relationships with mood or cognitive function in these patients using ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (¹⁸F-FDG-PET).

METHOD

A total of 40 consecutive adult patients with thyroid carcinoma who had undergone total thyroidectomy were recruited for this cross-sectional study. At the time of assessment, 20 patients were hypothyroid after two weeks of thyroid hormone withdrawal, while 20 received thyroid hormone replacement therapy and were euthyroid. All participants underwent brain ¹⁸F-FDG-PET scans and completed mood questionnaires and cognitive tests. Multivariate spatial covariance analysis and univariate voxel-wise analysis were applied for the image data.

RESULTS

The hypothyroid patients were more anxious and depressed than the euthyroid participants. The multivariate covariance analysis showed increases in glucose metabolism primarily in the bilateral insula and surrounding areas and concomitant decreases in the parieto-occipital regions in the hypothyroid group. The level of thyrotropin was positively associated with the individual expression of the covariance pattern. The decreased ¹⁸F-FDG uptake in the right cuneus cluster from the univariate analysis was correlated with the increased thyrotropin level and greater depressive symptoms in the hypothyroid group.

CONCLUSIONS

These results suggest that temporary hypothyroidism, even for a short period, may induce impairment in glucose metabolism and related affective symptoms.

Neural correlates of free T3 alteration after catecholamine depletion in subjects with remitted major depressive disorder and in controls

RATIONALE

Thyroid hormones and their interactions with catecholamines play a potentially important role in alterations of mood and cognition.

OBJECTIVES

This study aimed to examine the neurobiological effects of catecholamine depletion on thyroid hormones by measuring endocrine and cerebral metabolic function in unmedicated subjects with remitted major depressive disorder (RMDD) and in healthy controls.

METHODS

This was a randomized, placebo-controlled, and double-blind crossover trial that included 15 unmedicated RMDD subjects and 13 healthy control subjects. The participants underwent two 3-day-long sessions at 1-week intervals; each participant was randomly administered oral α-methyl-para-tyrosine in one session (catecholamine depletion) and an identical capsule containing hydrous lactose (sham depletion) in the other session prior to a [(18)F]-fluorodeoxyglucose positron emission tomography scan.

RESULTS

Serum concentrations of free T3 (FT3), free T4 (FT4), and TSH were obtained and assessed with respect to their relationship to regional cerebral glucose metabolism. Both serum FT3 (P = 0.002) and FT4 (P = 0.0009) levels were less suppressed after catecholamine depletion compared with placebo treatment in the entire study sample. There was a positive association between both FT3 (P = 0.0005) and FT4 (P = 0.002) and depressive symptoms measured using the Montgomery-Åsberg Depression Rating Scale. The relative elevation in FT3 level was correlated with a decrease in regional glucose metabolism in the right dorsolateral prefrontal cortex (rDLPFC; P < 0.05, corrected).

CONCLUSIONS

This study provided evidence of an association between a thyroid-catecholamine interaction and mood regulation in the rDLPFC.

Direct determination of ECD in ECD Kit: a solid sample quantitation method for active pharmaceutical ingredient in drug product

Technetium-99m ethyl cysteinate dimer (Tc-99m-ECD) is an essential imaging agent used in evaluating the regional cerebral blood flow in patients with cerebrovascular diseases. Determination of active pharmaceutical ingredient, that is, L-Cysteine, N, N'-1,2-ethanediylbis-, diethyl ester, dihydrochloride (ECD) in ECD Kit is a relevant requirement for the pharmaceutical quality control in processes of mass fabrication. We here presented a direct solid sample determination method of ECD in ECD Kit without sample dissolution to avoid the rapid degradation of ECD. An elemental analyzer equipped with a nondispersive infrared detector and a calibration curve of coal standard was used for the quantitation of sulfur in ECD Kit. No significant matrix effect was found. The peak area of coal standard against the amount of sulfur was linear over the range of 0.03-0.10 mg, with a correlation coefficient (r) of 0.9993. Method validation parameters were achieved to demonstrate the potential of this method.

Visualizing hormone actions in the brain

Profound and multifaceted effects of hormones on the development, maturation and function of the CNS are well documented. Recent developments in magnetic resonance imagining (MRI) and positron emission tomography (PET) permit detailed in vivo studies of cerebral structure and function in humans. Techniques to measure subtle differences in cerebral structure, regional brain activation, changes in blood flow and other physiological biomarkers allow us to translate experimental evidence of hormone effects obtained from animal models to humans. Here we review the imaging techniques available to support studies of hormone effects on the CNS, emphasizing the recent developments of MRI. In summarizing the major current studies we discuss the potential of these techniques for an emerging new field in endocrinology.

Brain glucose metabolism in hypothyroidism: a positron emission tomography study before and after thyroid hormone replacement therapy

CONTEXT

Hypothyroidism is frequently associated with subtle behavioral and psychiatric symptoms. The consequences of inadequate thyroid hormone availability to brain metabolism are poorly understood.

OBJECTIVE

This study assessed the relationships between neuropsychiatric symptoms and changes in relative regional cerebral glucose metabolism in hypothyroid patients undergoing thyroid hormone replacement therapy. DESIGN, SETTING, AND OUTCOME MEASURE: Relative regional cerebral glucose metabolism was compared in 13 previously untreated hypothyroid patients and 10 healthy control participants. Effects of thyroid hormone replacement therapy (levothyroxine, 3 months) were assessed using neuropsychiatric measures and positron emission tomography with [(18)F]fluorodeoxyglucose.

RESULTS

Before treatment, hypothyroid patients exhibited lower regional activity than control subjects in the bilateral amygdala, hippocampus, and perigenual anterior cingulate cortex (ACC), left subgenual ACC, and right posterior cingulate cortex. Severity of depressive symptoms covaried negatively with pretreatment activity in the bilateral middle frontal gyrus and right subgenual and dorsal ACC. Thyroid hormone replacement therapy abolished pretreatment group differences in regional activity, robustly increased activity in the ventral ACC, and significantly reduced both clinician-rated and self-rated behavioral and psychiatric symptoms. Increased activity within the ventral ACC was associated with reduced somatic complaints, whereas increased activity within the dorsal ACC was associated with reduced depressive symptoms.

CONCLUSIONS

Reduction of the behavioral complaints during thyroid hormone therapy is associated with a restoration of metabolic activity in brain areas that are integral to the regulation of affect and cognition. The findings suggest that thyroid hormone modulates regional glucose metabolism and psychiatric symptoms in the mature brain.

The thyroid-brain interaction in thyroid disorders and mood disorders

Thyroid hormones play a critical role in the metabolic activity of the adult brain, and neuropsychiatric manifestations of thyroid disease have long been recognised. However, it is only recently that methodology such as functional neuroimaging has been available to facilitate investigation of thyroid hormone metabolism. Although the role of thyroid hormones in the adult brain is not yet specified, it is clear that without optimal thyroid function, mood disturbance, cognitive impairment and other psychiatric symptoms can emerge. Additionally, laboratory measurements of peripheral thyroid function may not adequately characterise central thyroid metabolism. Here, we review the relationship between thyroid hormone and neuropsychiatric symptoms in patients with primary thyroid disease and primary mood disorders.

Imaging brain inflammation with [(11)C]PK11195 by PET and induction of the peripheral-type benzodiazepine receptor after transient focal ischemia in rats

[(11)C]PK11195 is used in positron emission tomography (PET) studies for imaging brain inflammation in vivo as it binds to the peripheral-type benzodiazepine receptor (PBR) expressed by reactive glia and macrophages. However, features of the cellular reaction required to induce a positive [(11)C]PK11195 signal are not well characterized. We performed [(11)C]PK11195 PET and autoradiography in rats after transient focal cerebral ischemia. We determined [(3)H]PK11195 binding and PBR expression in brain tissue and examined the lesion with several markers. [(11)C]PK11195 standard uptake value increased at day 4 and grew further at day 7 within the ischemic core. Accordingly, ex vivo [(3)H]PK11195 binding increased at day 4, and increases further at day 7. The PET signal also augmented in peripheral regions, but to a lesser extent than in the core. Binding in the region surrounding infarction was supported by [(11)C]PK11195 autoradiography at day 7 showing that the radioactive signal extended beyond the infarcted core. Enhanced binding was preceded by increases in PBR mRNA expression in the ipsilateral hemisphere, and a 18-kDa band corresponding to PBR protein was detected. Peripheral-type benzodiazepine receptor immunohistochemistry showed subsets of ameboid microglia/macrophages within the infarcted core showing a distinctive strong PBR expression from day 4. These cells were often located surrounding microhemorrhages. Reactive astrocytes forming a rim surrounding infarction at day 7 also showed some PBR immunostaining. These results show cellular heterogeneity in the level of PBR expression, supporting that PBR is not a simple marker of inflammation, and that the extent of [(11)C]PK11195 binding depends on intrinsic features of the inflammatory cells.

Assessment of alterations in regional cerebral blood flow in patients with hypothyroidism due to Hashimoto's thyroiditis

AIM

The aim of this study was to assess regional cerebral blood flow (rCBF) using detailed semiquantitative analysis of Technetium-99m hexamethylpropyleneamine (HMPAO) brain single-photon emission computerized tomography (SPECT) in patients with hypothyroidism due to autoimmune thyroiditis.

PATIENTS, MATERIAL AND METHODS

Twenty patients (mean age: 42+/-9 yr) and 12 control subjects (mean age: 35.4+/-8.5 yr) were included in this study. The corticocerebellar rCBF ratios were obtained from 52 cerebral areas on 6 transaxial slices. By using control group rCBF ratios, lower reference values (RLV) (average ratio -2 SD) were calculated and the regions below RLV having an rCBF ratio were considered as abnormal decrease (hypoperfused) areas.

RESULTS

Significant reduced rCBF rates were measured for 15 (29%) cortical regions for the patient group. The areas in which significant reduced rCBF were demonstrated in the patient group were as follows: a) in the right hemisphere: superior frontal (slice 1 and 2), inferior frontal (slice 1), anterior temporal (slice 1 and 2), precentral gyrus (slice 1 and 2), postcentral gyrus (slice 1 and 2), and parietal cortex; b) in the left hemisphere: superior frontal (slice 1 and 2), inferior frontal (slice 1), caudate nucleus, and parietal cortex. The hypoperfusion was calculated in 154 (14%, 94 right and 60 left) cortical regions out of 1040 regions in the patient group.

CONCLUSION

These findings indicate that the alteration of rCBF in patients with hypothyroidism due to Hashimoto's thyroiditis before T4 therapy can be demonstrated with brain SPECT. Additionally, the degree of rCBF abnormalities could be determined with brain SPECT in patients with hypothyroidism due to Hashimoto's thyroiditis with or without neurologic or psychiatric symptoms.