Colloid droplet accumulation precedes the enhancement of 6-keto-PGF 1 alpha release from the thyrotropin-stimulated thyroid gland.

Influence of thyrotropin (TSH) on colloid droplet formation in thyroid follicular cells and on release of a stable prostacyclin metabolite, 6-keto-prostaglandin 1 alpha (6-keto-PGF 1 alpha) from the thyroid has been studied in rats. Maximal accumulation of colloid droplets preceded the enhancement of the 6-keto-PGF 1 alpha release. Such a time sequence speaks against the possibility of prostacyclin involvement in the thyroid secretory response to TSH.