Sudden infant death syndrome and placental disorders: the thyroid-selenium link.

Placental insufficiency, inducing hypoxia-ischaemia, is considered a major cause of neuronal injury and impaired post natal development. Placental insufficiency alters the metabolism of arachidonic acid and its oxidation products. Premature labour and low-birth-weight infants are associated with reduced intrauterine blood-flow and infections of the reproductive tract. Thyroidal activity is depressed in undernutrition (placental insufficiency). Premature infants require extra vitamin C for normal tyrosine metabolism (tyrosine is the thyroxine precursor). Among the symptoms indicating infantile cretinism, which appear during 3-5 months of age are: delayed union of skull bones, torpid behaviour, slow feeding, cyanosis during feeding, excessive sleepiness, enlarged tongue, umbilical herniation, flabby musculature, short stature and delayed development. These symptoms have all been described in low-birth-weight infants and sudden infant death syndrome victims by various authors. Bacteria utilize selenium (at the expense of host tissue). Escherichia coli is among the bacteria invading the reproductive tract. E. coli produce thiouracil and are goitrogenic. Some strains of E. coli produce phospholipase A2 which releases arachidonic acid from phospholipids for prostaglandin synthesis. Phospholipase A2 is more active against peroxidized than non-peroxidized lipids. Bacterial competition for intrauterine selenium and goitrogenic bacterial infections of the reproductive tract during pregnancy, depress thyroid function in the fetus but not in the mother.