T3 rapidly regulates several steps of alpha subunit glycoprotein (CGA) synthesis and secretion in the pituitary of male rats: Potential repercussions on TSH, FSH and LH secretion

• T3 acutely decreases the Cga mRNA content while increases CGA protein content.
• T3 reduces the amount of Cga mRNA associated to ribosome.
• T3 rapidly reduces the CGA secretion in primary culture of anterior pituitary cells.
• T3 effects on CGA synthesis and secretion may have a repercussion on TSH, FSH and LH secretion.

TSH, FSH and LH share the same glycoprotein alpha chain (CGA) as part of their protein structure. Therefore, it is possible that thyroid and gonadal dysfunction may affect the CGA expression. This study evaluated several steps of CGA synthesis and secretion in thyrotrophs and gonadotrophs of control and hypothyroid rats, acutely or chronically-treated with T3. Hypothyroidism increased the Cga mRNA expression and its association to ribosome, but decreased intracellular CGA content. These parameters were reversed after acute or chronic T3 treatment. We conclude that T3 not only down-regulates Cga mRNA expression, as expected, but also inhibits the association of Cga mRNA to ribosome, as well as the CGA secretion. These findings add novel insights into our understanding of the role of T3 on the regulation of the Cga gene expression and CGA secretion, which might have a potential repercussion in all pituitary glycoprotein hormone synthesis and secretion.