Biological activity of the follicle-stimulating hormone (FSH) is dependent on its pattern of glycosylation and is altered during galactosemia, a genetic disease characterized by deficient activity of galactose-1-phosphate uridyltransferase (GALT). To assess the role of this enzyme in the synthesis of FSH, the expression of GALT at the mRNA and protein levels was measured in the whole anterior pituitary during the estrous cycle of rat. GALT was maximally expressed during the proestrous and estrous phases of the estrous cycle. The expression pattern of GALT was associated with gonadotropin-expressing cells. This close association is in accordance with the postulated role of GALT in modulating biological activity of FSH.