ACTH is a segment of a much larger glycoprotein prohormone molecule called proopiomelanocortin (POMC). POMC is synthesized by the corticotrophs of the anterior pituitary, which constitute about 10 percent of the gland.
Caviar harvested from an older fish is the more rare, and more sought after, white caviar. The Beluga sturgeon are primarily found in the Caspian Sea, which is surrounded by Iran, Azerbaijan, Russia, Kazakhstan and Turkmenistan. The other primary source of Beluga sturgeon is the Black Sea near Russia and Romania.
Osetra (Osciotr), the rare golden caviar (or Imperial caviar), comes from Acipenser guldenstaedti. These sturgeon range in size from 40 to 160 pounds. Although the golden caviar is highly prized, the eggs of this species are often more brownish in color.