Morphology, immunohistochemistry and morphometry of the thyroid gland in cases of sudden infant death syndrome (SIDS).

The thyroid glands of 107 SIDS victims (sudden infant death syndrome) have been studied. Controls consisted of 20 thyroid glands from infants who died of other causes (accidents, pneumonia etc.). The thyroid glands were investigated histologically, immunohistologically and morphometrically. Immunohistochemistry (S-100 protein and calcitonin) and morphometry showed no significant results. Histologically, hyperemia (severe: 34 cases = 31.8%; mild: 23 cases = 21.5%), and fibrosis (45 cases = 42.1%; mild: 26 cases = 24.3%) were found. A large number of cases showed depleted follicles (87 cases = 81.3%), little colloid (little: 37 cases = 34.6%; none: 9 cases = 8.4%) and desquamation (severe: 21 cases = 19.6%; abundant: 20 cases = 18.7%). Only fibrosis and depleted follicles were found more often in SIDS than in the controls (conditional logistic regression: rise of incidence for SIDS 2.9 times, P = 0.028, and 1.2 times, P = 0.051, respectively), a commoner occurrence of hyperemia in SIDS was of limited significance (P = 0.105). The alterations found can be taken as stress reactions to current or recurrent hypoxemia and the mild fibrosis indicates recurrent hypoxemia. All alterations indicate that the victims had previously suffered near death episodes. Even though the glands were handled with care, artefacts and autolysis must be taken into consideration. Neither the histological, immunohistological nor morphometrical studies of the thyroid gland gave an explanation as to the cause of death or showed any changes providing explicit help in diagnosing SIDS.