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Tsuji and Ito (2003) examined the thyroid functions of yusho
patients to study the chronic effects of the pathogenic
substances on thyroid functions. The examination was conducted
in a mass checkup on the 115 recognized yusho patients (48 men
and 67 women, average 63.3 years of age) in Fukuoka prefecture,
in which thyroid stimulating hormone (TSH), triiodothyronine
(T3) and thyroxine (T4) were determined by
electrochemiluminescence photometry. The subjects were
classified into a low level (blood PCB level < 2.3 ppb, 58
subjects) and high level (blood PCB ≥
2.3 ppb, 57 subjects) groups and the frequency of thyroid
dysfunction in them were compared.
Anomaly in at least one of the TSH, T3 or T4 levels was observed
in 20 cases out of 115 (17.4%). Low TSH was seen in 6 cases
(5.2%), high TSH in 13 (11.3%) and high T4 in 1 case (0.9%).
Anomaly of T3 level was not observed. In 13 cases T3 levels were
slightly higher but within the normal range as well as T4
levels; these subjects were diagnosed for latent thyroid
dysfunction. The blood PCB level was not correlated with TSH, T3
or T4 level. The frequencies of TSH anomaly in the high and low
level groups were not significantly different.
2. HCB
1) Cohort studies
Gocmen et al. (1989) conducted in an area in Turkey a
retrospective study on subjects who have a history of porphyria
about 20-30 years before from a population exposed to HCB in the
past. Enlargement of the thyroid was observed in 34.9% of the
subjects. No comparison was made with a control group.
2) Case-control study
No study in this category was found.
3) Synchronic studies
Sala et al. (1999) studied residents in an area near an
electrochemical plant where the atmospheric PCB level is high.
Randomly sampled subjects were examined for the blood HCB
levels. The average values for men were 9.0 ng/ml for those
without history of employment, 27.1 ng/ml for previous
employees, and 54.6 ng/ml for current employees. The results for
female counterparts were 14.9, 22.2 and 13.5 ng/ml,
respectively. The incident rates of thyroid dysfunction in
non-employees and previous employees were not significantly
different for either sex.
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