Tex. Ins. Code § 424.069

An insurer may invest the insurer's funds in excess of minimum capital and surplus in a loan on the pledge of any mortgage, stock, bond, or other evidence of indebtedness acceptable as an investment under Sections 424.051, 424.053-424.071, and 424.074, if the current value of the mortgage, stock, bond, or other evidence of indebtedness is at least 25 percent more than the amount of the loan.