Doctors at Mexico City’s Central Military Hospital plan to remove a thyroid nodule during the July 31 operation, after which Peña Nieto will have a four-day recovery period at Los Pinos, the MexicanWhite House.

The thyroid gland is in the neck, below the voice box. Among other things, it helps regulate metabolism.

According to the American Thyroid Assn. website, thyroid nodule removal surgery may be necessary for a number of reasons. A biopsy may have determined that the nodule is cancerous, or possibly cancerous. Surgery may also be necessary if a biopsy was inconclusive. Nodules known to be non-cancerous may need to be removed if they are large, or causing pain.

The statement from the president’s office did not say which of these might be the case for Peña Nieto, and a spokesman declined to comment.

Peña Nieto, of Mexico’s Institutional Revolutionary Party, or PRI, was elected in July 2012 and took office in December. He is pressing for a series of proposed institutional reforms that he says are designed to make Mexican government more modern and efficient.

this month, he finished a Mexico City 10K road race (6.2 miles) in a respectable 54 minutes, 8 seconds.