All persons granted a disability retirement allowance shall undergo such examination, from time to time, as the board or medical panel may designate and any disability beneficiary who has not yet attained his minimum service retirement age and time, who refuses to submit to such examination, shall forfeit his right to draw any retirement allowance and the same shall be discontinued. A member retired on a disability retirement allowance shall submit to the board, for such period as the board may require, sworn statements of all income for labor, services or employment performed by such member during the time of said member's disability retirement.
T.C.A. § 8-3508