The board may require any member who has applied for or is receiving disability benefits under this article to submit to a physical examination, mental examination or both, by a physician or physicians selected or approved by the board and may cause all costs incident to the examination and approved by the board to be paid from the fund. The costs may include hospital, laboratory, X-ray, medical and physicians' fees. A report of the findings of any physician shall be submitted in writing to the board for its consideration. If, from the report, independent information, or from the report and any hearing on the report, the board finds that the member is no longer totally disabled and is engaged in or is able to engage in substantial gainful employment, then the disability benefits shall cease. The board shall require recertification annually for the first three years of disability and thereafter at the discretion of the board. For purposes of recertification the board may require a disability retirant to undergo a medical examination to be made by or under the direction of a physician designated by the board, or to submit a statement signed by the disability retirant's physician certifying continued disability, and may require the retirant to submit copies of annual income tax returns. If a retirant refuses to submit to medical examinations or to provide statements or returns requested for recertification, the board may discontinue disability until the retirant complies.