ORIGINAL ARTICLE
Annals of Nuclear Medicine Vol. 18, No. 6, 469-477, 2004

Cerebral blood flow abnormalities induced by transient hypothyroidism
after thyroidectomy
mAnalysis by Tc-99m-HMPAO and SPM96
Shigeki NAGAMACHI,*Seishi JINNOUCHI,*Ryuichi NIsnlI,*,**** Yasushi ISHIDA,**Seigo FUJ1TA,*
Shigemi FUTAMI,*Takao KODAMA,*Shozo TAMURA*and Keiichi KAWAI***'*****Department of Radiology, Miyazaki Medical College**Department of Psychiatry, Miyazaki Medical College***School of Health Science, Faculty of Medicine, Kanazawa University****Division of Radiopharmaceutical Chemistry, Biomedical Imaging Research Center, Fukui University

The current study is an investigation of alterations in regional cerebral blood flow (rCBF)
distribution in patients with transient hypothyroidism after thyroidectomy. In addition, the effectsof thyroxine treatment on rCBF changes were studied. Methods: Noninvasive rCBF measurements
using 99mTc-HMPAO SPECT were performed on 24 post-thyroidectomy patients who were in ahypothyroidic state. The measurements were conducted before 131I therapy and after thyroid
hormone (thyroxine) replacement. We used adjusted rCBF images (normalization of global CBF
for each subject to 50 ml/100 g/min with proportional scaling) to compare these data with agematched normal control groups (n =15) using SPM96. We also compared the absolute rCBF valueof hypothyroidic patients with those of normal control groups. In addition, the association between
rCBF alteration and the severity of depression was also analyzed. Finally, the effect of thyroid
hormone replacement on rCBF was investigated individually using the Jack-knife test, in which
patient data were compared with those from healthy volunteers. According to the result of this test,
all cases were categorized into three subgroups, namely, improved, unchanged group and normal.
To prove the reversibility of rCBF alteration after thyroid hormone replacement, a group comparison test between the normal controls and the improved group was done before and after thyroid
hormone replacement. Similarly a group comparison test between the unchanged group and normal
controls was also performed. Results: In the hypothyroidic condition, there was a significant
decrease in the posterior part of the bilateral parietal lobes and in part of the bilateral occipital lobes,
including the cuneus. These decreased rCBF areas extended to the bilateral prefrontal cortices as
deterioration became more profound. On individual analysis, 16 of 24 patients (66.7%) demonstrated rCBF reduction, while 8 patient did not show significant rCBF change (33.3%, the normalgroup). After thyroxine replacement, improvement ofrCBF was noted in nine of 16 patients (56.3%,
the improved group). In seven of 16 patients (43.7% the unchanged group), the significant low rCBF
area remained unchanged. Compared with the normal controls, the improved group showedsignificantly decreased rCBF of the bilateral parietal lobe and the occipital lobe in the hypothyroic
condition. After thyroid hormone replacement, these abnormal rCBF areas disappeared. In contrast,in the unchanged group, the significant hypoperfusion area became localized but remained.
Conclusion: 99mTc-HMPAO SPECT and SPM96 analysis demonstrated a significant rCBF
decrease in the parietal lobe and part of the occipital lobe in patients with induced transienthypothyroidism after thyroidectomy. This phenomenon might contribute to understanding of thedepressive state. Recovery of rCBF after thyroid hormone replacement was confirmed in someReceived Mey 27, 2003, revision accepted April 19, 2004.
For reprint contact: ShigekiNagamachi,M.D., Departmentof
Radiology,Miyazaki Medical College, Kihara 5200, Kiyotake,Vol. 18, No. 6, 2004

Miyazaki 889-1692, JAPAN.
E-mail: snagama@post1.miyazaki-med.ac.jp

Original Article 469

patients. However, rCBF improvement did not always occur in every patient during the follow up
period. The reversibility of rCBF in transient hypothyroidism may be dependent on individual
characteristics during a short-term period.
Key words: 99mTc-HMPAO, regional cerebral blood flow, transient hypothyroidism, SPM96(statistical parametric mapping), thyroxin replacement therapy, post-thyroidectomy~TRODUCTION
HYPOTHYROIDISMis associated with disturbances in moodand intellectual function. 1-3 Because of the close relationship between these psychiatric conditions and cerebral
blood flow (rCBF), it is possible that thyroid hormone
depletion could result in an alteration of rCBF. Previously, the rCBF of hypothyroidic patients with apparent
clinical psychiatric symptoms was reported to be decreased. 4-6 However, the rCBF changes related to induced transient hypothyroidism, such as pre-131I-therapy
conditions, remain unclear.
Because 131Itherapy after total thyroidectomy is sometimes problematic due to psychiatric disturbances, theassociation between the symptom and the rCBF alteration
should be elucidated. Recently, Constant et al. reported
that diffuse rCBF reduction and decreased glucose metabolism could be observed by PET studies even in
induced hypothyroidism.7
To confirm the previous report using more convenient
SPECT equipment, we performed 99mTc-HMPAO SPECT
to investigate the relationship between this psychiatricissue and rCBF changes in the short-term hypothyroidic
state before 131I therapy. The reversibility of possible
rCBF alterations by thyroid hormone replacement after
1311therapy was also investigated. We applied SPM96(statistical parametric mapping) analysis to avoid subjectivity, such as intensive ROI placement to establish differences with normal tracer distribution on functional
activity maps. 8,9
MATERIALS AND METHODS

Subjects
We studied 24 patients who had undergone total thyroidectomy due to thyroid cancer (6 men, 18 women;mean age: 55.4 years; range: 23-76 years). All patientswere hospitalized for 131I therapy. For 14 of the 24
patients, this was the first use of 131Iirradiation therapy
after thyroidectomy. For six patients, it was the second
time, and for four, it was the third time. The period
between the baseline study and thyroidectomy was longer
than 40 days at least (53.5 + 12 days). All patients were
free of thyroid hormone replacement therapy at least 3
weeks before the baseline study. Hypothyroidism wasdiagnosed by serum T4 (mean value: 2.0 + 2.9/lg/dl), T3(mean value: 0.33 + 0.28 ng/m/), and TSH (mean value:

470 ShigekiNagamachi, Seishi Jinnouchi, Ryuuichi Nishii, et al

120.1 + 86.2/.tlU/ml). Patients with a history of known
cerebro-vascular disease or psychiatric disease were excluded. All subjects underwent MRI examinations, andpatients with organic lesions were excluded.
A self-assessment test for depression (SDS) was doneto evaluate their psychiatric condition. Although eachsubjects was free of apparent typical symptoms, such as
apathy, their scores on the SDS test categorized them assuffering from mild (<39), moderate (40--49), or severe(<50) depression or neurosis. Fifteen control subjects (8men, 7 women; mean age, 56.7 years; range: 32-76 years)
were also studied. They were healthy volunteers who had
no neurological or psychiatric disorders, including alcoholism, substance abuse, atypical headache, head trauma,
or asymptomatic cerebral infarction detected by T2weighted MRI. The portion of the study involving healthy
volunteers was approved by the ethics committee ofMiyazaki Medical College. All healthy volunteers and all
patients gave informed consent. After the course of 131I
therapy, all subjects were restored to the euthyroidic
condition by thyroxine replacement. The follow-up studies were performed in the euthyroidic state. The mean
period between the baseline study and the follow-up study
was 71.6 + 37.4 days.

Brain SPECT procedure
Before undergoing SPECT, all subjects received an intravenous line while lying down with their eyes closed. Eachsubject received a 600 MBq intravenous injection of
99mTc-HMPAO (PAO). A dynamic study was done forcalculating absolute rCBF value using graphic analysis.l~
Ten minutes after this injection, the brain SPECT was
performed using a triple-head gamma camera (Prism
3000: Marconi) equipped with a high-resolution fanbeam
collimator. For each camera, projection data were obtained in a 128 x 128 format for 24 angles of 120~ at 50s
per angle. A Shepp and Logan Hanning filter was used for
SPECT image reconstruction at 0.7 cycle per centimeter.
Attenuation correction was performed using Chang's
method.

Image analysis
The image data were analyzed using SPM96. Prior to
statistical analysis, all of the images were spatially normalized into the standard template developed by Ohnishi
et at. to remove the inter-subject anatomical variability.11
Statistical parametric maps, which are spatially extended

Annals of Nuclear Medicine

b Comparison of rCBF between transient hypothyroidism (whole
patients) and control
Fig. 1 SPM map showing significantly lower rCBF in transient hypothyroidism in comparison withhealthy volunteers. Notice the decrease of rCBF in the posterior part of the bilateral parietal lobe, righttemporal lobe and bilateral cuneus (a). Compared to the normal control, patients with transienthypothyroidism demonstrated relatively decreased global rCBF. However, it was not statisticallysignificant. They also showed relatively lower rCBF in prefrontal area, temporal lobe, parietal lobe andoccipital lobe (b).

statistical processes, were used to characterize regionallyspecific effects in imaging data. We used the adjusted
rCBF images (normalization of global CBF for eachsubject to 50 ml/lO0 g/rain with proportional scaling) toevaluate the alteration of the relative rCBF distribution in
the transient hypothyroidic patients. The resulting set ofvalues for each comparison constituted a statistical parametric map of the t statistic SPM {t }. The SPM {t } maps
were then transformed to the unit of normal distribution(SPM {z}) and reached a threshold at p -- 0.01. The
resulting regions were examined using multiple comparisons. The significance of each region was estimated at athreshold ofp = 0.01 using distributional approximations
from the theory of Gaussian fields.12 Anatomic localization was done according to the atlas of Talairach andTournoux 13 using a set of linear transformations. 14At thesame time, the absolute value of rCBF was also analyzed
in a transient hypothyroidism condition. Global rCBF of
the cerebrum was calculated by the Patlack plot analysis,
and the rCBF of each territory was obtained using
3D-SRT software developed by Takeuchi, et al. 15 In thestatistical analysis, we used the non-parametric KruskalWallis test to assess the difference between each group. A
p value of < 0.05 was considered to be significant.
The analyzed issues were as follows.
(1) To elucidate the influence of induced hypothyroidism on rCBF alteration, a group comparison of rCBF
distribution between the transient hypothyroidic patients(n = 24) and the healthy volunteers (n = 15) was performed
using SPM. The absolute values of global rCBF and rCBF
in 4 territories (pre-frontal, parietal, temporal and occipital) between all hypothyroidism patients and normal controls were also compared.

Vol. 18, No. 6, 2004

Table I Hypothyroidism vs. control subjects
Anatomical location

Maximal Z score

Left. inferior parietal lobule
Right. precuneus
Left. cuneus

5.6
5.6
5.3

Table 2 The severity of depression and rCBF pattern
DepressionMild(n = 8)Anatomical location

MaximalZ score

Left. cuneus
Right.inferior occipital gyrus
Left. inferior parietal lobule
Moderate Left. inferior parietal lobule(n = 9)Right.paracentral lobule
Left. paracentrai lobule
SevereRight.precuneus(n = 7)
Left. cuneus
Right. paracentral iobule

4.63
4.46
4.31
5.41
5.06
4.97
4.72
4.69
4.05

(2) To analyze the possible association between theseverity of depression and rCBF alteration, a comparisonof rCBF distribution between the healthy volunteers andeach subgroup (severe, moderate and mild case of depression) classified by depression score (SDS) was conducted. In addition, the absolute rCBF value between
normal controls and each subgroup was also compared.
(3) To evaluate the serial rCBF change individually,
the Jack-knife test was done by comparing the data withthe healthy volunteers before and after thyroid hormone
replacement. Based on the results, all cases were categorized into three subgroups, namely, improved, unchanged
and normal. The improved group is composed of patients

Original Article 471

b Comparison of rCBF between transient hypothyroidism (subgroup) andcontrol

Fig. 2 With an increase in the severity of depression, a significant hypoperfusion area extended to the prefrontal cortex. Every subgroup showed asignificant reduction of rCBF in the bilateral precuneus, cuneus, and inferiorparietal lobe (Upper row: mild stage group, Middle row" moderate stage
group, Lower row: severe stage group) (a). In a comparison of the subgroups
with transient hypothyroidism and normal control, both the moderately andseverely depressed individuals showed significantlydecreased global rCBF.
They also demonstrated a significant rCBF reduction in the parietal lobe andoccipital lobes. Significantly decreased rCBF in the prefrontal area was also
noted in the severely depressed patients (b).
who improved and attained the same rCBF levels as thosein the normal controls after thyroid hormone replacement.
The unchanged group included patients with significantly
decreased rCBF on the baseline study who still showedsignificant hypo-perfusion after thyroid hormone replacement. The normal group included patients whose rCBF
did not show any statistical significance compared withnormal controls in the baseline study and in the follow-up
study after thyroid hormone replacement.
(4) To confirm the possible reversibility of rCBF
alteration after thyroid hormone replacement, a groupcomparison study between the normal controls and theimproved group was done before and after thyroid hormone replacement. Similarly, a group comparison test
between the unchanged group and the normal controls
was also performed.
(5) Finally, to determine the clinical factors that were
influential for the reversibility of rCBF, the mean value ofage, T3, T4, TSH, SDS score, and duration between theserial studies were compared among the three subgroupsof patients (improved, unchanged and normal).
RESULTS(1) Transient hypothyroidic patients revealed a significant decrease in rCBF in the parietal (inferior parietal
gyrus and precuneus) and the occipital lobes (cuneus)(Fig. la, Table 1). The global absolute rCBF was relatively lower but not statistically significant in transient472 ShigekiNagamachi, Seishi Jinnouchi, Ryuuichi Nishii, et al

Fig, 3 Forty-five-year-old woman. Improved case. Semm T3,
T4, and TSH (0.4 ng/ml, 1.8/.tg/dl, 120/.dU/m/) changed to thenormal range (1.1 ng/ml, 10.3 ~g/dl, 0.1 uIU/m/) after thyroid
hormone administration. On the 99mTc-HMPAOSPECT using
SPM analysis by the Jack-knife test, there was significantly
decreased rCBF in the bilateral posterior lobe, posterior lobe,
and bilateral superior temporal lobe in the hypothyroidic condition (upper). These decreased rCBF area improved after thyroid
hormone therapy (lower).

Annals of Nuclear Medicine

hypothyroidic patients compared to that in normal controls. The regional rCBF in prefrontal region, temporal,
parietal and occipital lobes also showed no statisticalsignificance between the hypothyrodic patients and normal controls either (Fig. lb).
(2) In the group with a mild stage depression, significant hypoperfusion areas were noted in the left cuneus andin the bilateral posterior part of the parietal lobe and partof the bilateral temporal lobes. Similarly, the bilateralposterior part of the parietal lobe was also noted as asignificant hypoperfusion area in the group with moderate
depression. In the group with severe depression, significant
hypoperfusion areas extended to the bilateral prefrontal
areas in addition to the left cuneus and bilateral posteriorpart of the parietal lobe. The significantly decreased rCBF
area extended to the prefrontal area as the severity ofdepression advanced (Table 2, Fig. 2a). The result wasquantitatively confirmed by the absolute value. Within
the hypothyroidism subjects, both groups, those withsevere and moderate depression, showed significantly
lower rCBF of the global, bilateral parietal, and bilateral
occipital lobes than did those in the normal control group.
Significant rCBF reduction in the prefrontal area was also
noted in the severely depressed patients (Fig. 2b).
(3) Nine of 24 patients (37.5%) were categorized as
improved (Fig. 3). Seven of 24 patients (29.2%) were
unchanged, and the normal group had 8 (33.3 %) patients(Table 3).
(4) The improved group showed significantly reducedrCBF of the bilateral parietal lobes and occipital lobe in
the hypothyroic condition. After thyroid hormone replacement, these abnormal rCBF area disappeared (Table
4, Fig. 4). In contrast, in the unchanged group, a significant
hypoperfusion area became localized but remained after
thyroid hormone replacement (Table 4, Fig. 5).
(5) In comparison study (unpaired t-test) between the
improved group and the unchanged group, there was no
statistical significance in the mean value of age, T3, T4,
TSH, and SDS score, and duration between the serial
studies (Table 5).

Table 3 Subgroup according to the effect of thyroid hormone
replacement
9The improved group:
Decreased rCBF with improvement
after thyroid hormone replacement
9The unchanged group:
Decreased rCBF with no significant
change after thyroid hormone
replacement
9The normal group:
No abnormalities in hypothyroidism
condition

n=9(37.5%)

n=7(29.2%)

n=8(33.3%)

Fig. 4 Tc-99m-HMPAO SPECT with SPM analysis in patientswith the improved group. In the hypothyroidic condition(upper), there was significantly decreased rCBF in the bilateralparietal and bilateral occipital lobes. These decreased rCBF
areas improved and disappeared after thyroid hormone replacement (lower).

Table 4 Comparison between the improved group and unchanged group
Improved group (n = 9)
Hypothyroidic condition

Unchanged group (n = 7)
Hypothyroidic condition

Euthyroidic condition

Vol. 18, No. 6, 2004

Anatomical location

Maximal Z score

Left inferior parietal lobule
Right precuneus
Right cuneus

4.75
4.44
4.38

Right supra marginal gyrus
Right inferior parietal lobule
Left cuneus
Left cuneus
Right cuneus
Right precuneus

4.68
4.47
4.38
4.16
3.96
3.87

Original Article 473

Fig. 5 Tc-99m-HMPAO SPECT with SPM analysis in patientsin the unchanged group demonstrated persistently decreased
perfusion in both the parietal and occipital lobes even after
thyroid hormone replacement therapy (upper). However, thesesignificantly low perfusion areas became localized and decreased more in size than those in condition with transienthypothyroidism (lower).

Table 5 Comparison of clinical factors

Age (y)T3 (ng/ml)
T4 (ug/dl)
TSH (/zlU/m/)Interval (day)SDS change

Improvedgroup(n = 9)Unchanged
group(n = 7)

Normalgroup(n = 8)53.8 + 17.3
1.3 + 0.7
10.3 + 3.7
0.2 + 0.08
77.3 + 32.1
8.4 + 2.4

57.6 + 5.3
1.1 + 0.8
9.3 + 3.3
0.3 + 0.07
66.5 + 28.3
7.5 + 2.6

52.6 + 7.7
1.1 + 0.8
10.2 + 2.3
0.3 + 0.06//

T3, T4, TSH: Mean values at follow-up study
Interval: Mean intervals from the baseline study
SDS change: Change of the depression score value between theserial studies

DISCUSSION

The current study showed a significant decrease in rCBF
by SPM analysis in the short duration of induced transienthypothyroidism before laq-therapy. In the quantitative
analysis, the reduced rCBF was noted in the bilateralparietal, occipital and frontal lobes in patients with moderate or severe depression. The result agrees partially witha previous report regarding the decrease of rCBF in
induced hypothyroidism by a PET study. 7
Mental condition is a major factor in determining rCBF
distribution. 6,16,17Patients with hypothyroidism are moredepressed than those with euthyroidism. Previous reports
have indicated that depression induces a reduction in

474 Shigeki Nagamachi, Seishi Jinnouchi, Ryuuichi Nishii, et al

rCBF in the left anterior cingulate and left dorsolateralprefrontal cortex.18,19However, in the current study, mostpatients showed significant hypoperfusion in the inferiorparietal lobe, precuneus, cuneus. They did not show
significant hypoperfusion in the frontal lobe or anterior
cingulate gyrus related to depression. The result agrees
partially with a report by Constant et al., in which theyrefer to a trend toward reduced glucose metabolism in theinferior parietal lobe. 7 The parieto-occipital lobe is one of
the regions associated with the organization of language
when listening, speaking, or writing. The psychiatricmanifestations of hypothyroidism have many aspects,
including psychomotor slowing, 2~depression, 21 and anxiety. 21 Cognitive dysfunctions with alterations in attention, concentration, perception, and speed of thought
were also common clinical manifestations. 22 As no patients were subjected to cognitive examinations, such as
the mini mental state examination (MMSE), the exact
cause of low perfusion in these areas could not be validated. Although symptoms were not always manifested,a few patients complained of impaired reading or writing
ability. However, latent cognitive dysfunctions might
exist in an induced hypothyroidic condition. Significant
reduction of rCBF in the posterior part of the parietal lobe
should be associated with cognitive dysfunctions. A cognitive function test or SPECT with a cognitive function
task might be preferable to validate the relationship to thechange of rCBF.
Both precuneus and cuneus play a role in vision-related
functions. However, no patients revealed visual dysfunctions, such as hallucinations or optic ataxia. 23 In previous
research, a trend has been reported toward reduced rCBF
and reduced glucose metabolism in the left cuneus at alower statistical level.7 A detailed study of visual activity
and perception in hypothyroidism, combined with a neurochemical and neuropathological study of the cortex
related to visual ability, is required.
Interestingly, there was no significant reduction ofrCBF in the prefrontal area, although these changes areusually described in depressed patients. On the other
hand, the reduced rCBF area was larger in the severely
depressed group than in other groups, and these low
perfusion area tended to extend to a part of the prefrontal
area in individuals in the severely depressed group. As
described above, latent cognitive dysfunction should be
related to these phenomena. The depressive state might be
induced secondary by these cognitive dysfunctions. Therefore, the positive association between the prefrontal rCBF
and the severity of the SDS score was partially considered. Because the depression of the subjects in the current
study was relatively mild, the prefrontal area was assumed to be preserved in the group comparisons between
all the subjects and the normal controls. A respective
subgroup comparison according to the SDS score waspreferable to confirm the association between depressive
symptoms and the rCBF change in the prefrontal cortex in

Annals of Nuclear Medicine

induced transient hypothyroidism.
The insignificant rCBF improvement in about onethird of the patients after thyroxine replacement suggeststhat thyroid hormone replacement therapy is ineffective
for the recovery of rCBF alteration during the short term.
The current result was partly supported by a report from
Pollock et al., which showed that thyroxine did not restore
cognitive function.24 However, these results are in contrast with previous studies, in which thyroxine treatment
was associated with psychological improvement.6'12'16'17
One possible explanations of the result is the severity ofthe patients' hypothyroidism. Clinically apparent psychiatric conditions in severe hypothyroidism were improvedby thyroxine. 6 However, a slight modification in the
subclinical psychiatric condition, such as in the current
study, might not be detected. On the other hand, by theJack-knife test, 56.3% of the cases showed improvement
to some extent after thyroxine replacement. Although
the effective factor could not be determined, age andthe duration of the thyroxine replacement period wereconsidered to be related. In addition, repetitive induced
hypothyroidism could cause severe neuronal damage.
The amount of 131Itherapy, therefore, could also be an
influential factor.
About one third of all the subjects showed a normalrCBF range under the hypothyroidic condition. Although
no prominent characteristics were found, most of thesesubjects included relatively, but not significantly, younger
patients. Aging might be the determing factor in the
reduction of rCBF in transient hypothyroidic conditions.
This speculation needs to be confirmed in a comparison
study with a larger group of age-matched controls.
Although we used the normalized rCBF to remove thedifferences in global CBF between the individuals, there
are some possible disadvantages to using SPM96 in
SPECT image analysis, which include its lack of validation and the limited number of scans involved in a typical
SPECT study (often less than 30). As a result, somestudies may not have sufficient statistical power to accurately control for a false negative result in areas showing
no significant differences between patients and controls.25
Although the SPM technique is useful for objective investigations, further analysis in a larger population will
clarify the issue. At the same time, to prevent the confounding factor of primary psychiatric disease, a preoperative SPECT scan would have improved the study
design with a better comparison.
In the normalization process of all subjects prior to
statistical analysis, we used the ECD template./l The
rCBF distribution is different between ECD and HMPAO
in the same standard brains, namely, HMPAO SPECT
showed relatively higher uptake in the medial temporal
lobes, thalami, periventricular white matter. 26 However,anatomical distribution is almost the same between thetwo radiopharmaceuticals. Therefore, statistical analysis
in the standard brain, smoothed and globally normalized

Vol. 18, No. 6, 2004

in the same template was considered to be possible.
However, Gispert et al. reported that using the standard
template with different tracer may lead to inconsistentinterpretations of the SPM analysis.27 Ideally, a standard
template with HMPAO should be used for strict analysis.
In addition, HMPAO has the limitation of soft tissue,
which causes contamination by scattering X-rays. In
particular, a tumor or inflammation of extra-cranial skintissue may cause a localized increased uptake. 28Although
there were no cases in the current study of cases with ahigh tracer uptake in extra-cranial skin tissue, the influenceof the background could not be ignored. Tracers with asmall background, such as ECD, would be preferable infuture research.
One more issue is the influence of hypothyroidism on
cardiac contractility.29-31 Because rCBF is affected bycardiac functions,32-34 the current data could not exclude
the influence of impaired cardiac contractility. However,
all of the patients underwent a whole body MIBI scintigraphy to diagnose metastasis before I-131 therapy. 35
Because the MIBI-gated myocardial SPECT performedat the same time showed normal left ventricular wallmotion and normal LVEF value in all cases, it was
assumed that there was no influence of hemodynamic
failure. Future study should include a categorization ofcases according to myocardial functions.
CONCLUSION
The current study demonstrated that there was a significant
decrease of rCBF in transient hypothyroidism in thebilateral precuneus, inferior-parietal lobe, and cuneus incomparisons with healthy volunteers. As the severity ofdepression in transient hypothyroidism advanced, these
decreased rCBF area extended to the frontal lobe. The
results suggested that both depression and cognitive dysfunction influenced the rCBF alteration.
After thyroid hormone replacement, some cases revealed prominent rCBF improvement, others showed
fixed or prolonged decreased rCBF. Recovery of rCBF intransient hypothyroidism after total thyroidectmy, therefore, may be dependent on individual characteristics
during a short-time period.
Additional studies are needed to confirm whether thecurrent results are applicable to other hypothyroidic conditions.
ACKNOWLEDGMENTS
This work was supportedin part by the Grant-in-Aidfor Scientific
Research (#12670890) of Japan Society for the Promotion of
Science.
The authors thank the technical staff for their assistance,
Hideo Arita and Keishi Takayama at MiyazakiMedical College
for data acquisition, and Yoshihiro Tahara for developing thefigures.

Original Article 475

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