Influence of dietary habits on thyroid status of a nomadic people, the Bororo shepherds, roaming a central African region affected by severe iodine deficiency

Abstract

OBJECTIVE: In contrast with the endemic goiter reported in several African countries, the nomadic Bororos of the Central African Republic have an unexpectedly low prevalence of goiter. This study was conducted to elucidate this puzzling observation. DESIGN: Thyroid function and iodine and thiocyanate intakes were evaluated in Bororos and inhabitants of the same area and compared with an Italian population. RESULTS: Urinary iodine concentrations indicated moderate iodine deficiency in the rural people and the Bororos. In the latter, no individual with clinical hypothyroidism was observed. Compared with the reference population, the Bororos had slightly lower thyroxine (T4) and free thyroxine (FT4), slightly increased tri-iodothyronine (T3) and T3/T4 ratio, slightly higher TSH, normal serum thyroglobulin, a prevalence of goiter of 17.1% and a higher urinary thiocyanate. The rural people showed striking differences: lower T4 and FT4, increased T3/T4 ratio, markedly increased TSH and thyroglobulin, a prevalence of goiter of 76.9% and a high urinary thiocyanate, indicating frequent consumption of cassava. A dietary survey indicated that the Bororos ingest large amounts of milk and related products but infrequently eat cassava. CONCLUSION: A minute difference in iodine deficiency between two populations induces totally different patterns of goiter and thyroid function. The reason for such a contrast probably involves differences in diet.