Background: There is paucity of data on the relationship between
thyroid hormones, potassium and eclampsia. Moderate-to-severe iodine deficiency
that worsens during pregnancy leads to decreased thyroid hormone output and
bioavailability to the brain. Apart from metabolic functions, T3 and T4 are
essential fast acting cytosolic and synaptosomal neural transmitters that also
regulate neuronal excitatory-inhibitory mechanisms. T3 also regulates the Na
-K -ATPase pump that maintains the membrane ionic gradient. Hence
altered serum potassium, thyroxine and triiodothyronine levels could increase the
risk of eclamptic seizures. Methods: Forty-five women with eclampsia, 45
severe preeclampsia and 90 normotensive pregnant controls were enrolled into this
study. Levels of thyroid hormones, thyroglobulin and urine iodine concentration
(UIC) were measured and compared between the three groups. Results:
Eclamptic participants had significantly lower median serum potassium (K),
triiodothyronine (FT3), urinary iodine concentration (UIC) but higher serum
thyroglobulin (Tg) (K = 3.7 mmol/L; FT3 = 3.8 pmol/L; UIC = 69.5
g/L; Tg = 39.0 g/L) than normotensive pregnant
controls (K = 4.3 mmol/L; T3 = 4.7 pmol/L; UIC = 169.5 g/L; Tg =
19.5 g/L) and participants with severe preeclampsia (K = 4.2
mmol/L; T3 = 4.4 pmol/L; UIC = 95.7 g/L; Tg = 22.4
g/L), p 0.05. Low UIC, low serum T3 and potassium and
elevated Tg were independent predictors of eclampsia. Conclusions: Women
with iodine deficiency in pregnancy may be at increased risk of eclampsia
secondary to the ensuing rapid peripheral turnover of thyroid hormones leading to
hypothyroxinaemia and reduced triiodothyronine bioavailability to the central
nervous system that can be exacerbated by hypokalaemia.