An insurer has started to use its authority to invest in its own shares.

The board of Protective Life Corp., Birmingham, Ala., set aside $100 million for stock repurchases in May 2007. That authorization will extend through May 2010, the company says.

Protective Life began Tuesday to make actual stock purchases using that stock repurchase authorization, the company says.

“Future repurchase activity will be dependent on many factors, including market conditions, capital adequacy and the relative attractiveness of alternative uses of capital,” the company says.