Iowa Code § 497.8: Amending articles.

The association may amend its articles of incorporation by a majority vote of its stockholders at any regular stockholders’ meeting, or at any special stockholders’ meeting called for that purpose, on ten days’ notice to all stockholders. Said power to amend shall include the power to increase or diminish the amount of capital stock and the number of shares; provided the amount of the capital stock shall not be diminished below the amount of paid-up capital at the time the amendment is adopted.