Neonatal administration of MSG leads to
a syndrome of endocrine dysfunction characterised
by reduced growth, obesity and hypogonadism. The aim
of the present investigation was to gain information
on the structure and function of the pituitary-thyroid axis
in MSG-treated rats. Neonatal Wistar rats received
an S.C. MSG (4 mglg body weight) or hyperosmotic
saline (controls) on days 2, 4, 6, 8 and 10 of life.
Histological and morphometrical studies were carried
out on the thyroids of rats during the 4th month of life.
Plasma TSH, T3, and T4 were measured by RIA kits.
MSG-treated rats showed stunted growth, obesity and
decreased pituitary weight. MSG administration resulted
in increases in thyroid weight, absolute volumes
of epithelium, colloid and stroma, and blood T3 level
while T4 level remained unchanged. In enlarged thyroid
gland, percentage fractions occupied by epithelium,
colloid and stroma were similar to those observed in
control rats.
The results obtained suggest that the rat hypothalamic
centres involved in regulation of the pituitary-thyroid
axis are slightly affected by neonatal MSG treatme