40 ILCS 5/16-163
A board of 15 members constitutes the board of trustees authorized to carry out the provisions of this Article and is responsible for the general administration of the System. The board shall be known as the Board of Trustees of the Teachers' Retirement System of the State of Illinois. The board shall be composed of the Superintendent of Education, ex officio; 7 persons, not members of the System, to be appointed by the Governor, who shall hold no elected State office; 5 persons who, at the time of their election, are teachers as defined in Section 16-106, elected by the contributing members; and 2 annuitant members elected by the annuitants of the System, as provided in Section 16-165. The president of the board shall be appointed by the Governor from among the trustees.
40 ILCS 5/16-163