* Q2 profit 437 mln pesos vs yr ago 106 mln pesos
* Revenue up 21 pct at 16.3 bln pesos
MEXICO CITY, July 25 (Reuters) - Mexican corn miller and tortilla maker Gruma on Wednesday posted a four-fold increase in its second-quarter profit, helped by gains on currency derivatives and lower financing costs for its debt.
Profit soared to 437 million pesos ($32.8 million) from 106 million pesos in the year-earlier period.
Second-quarter revenue rose 21 percent to 16.3 billion pesos from 13.5 billion pesos last year, boosted by higher prices.
The company said the derivative gains were related to currency hedges used to manage corn purchases. Gruma also paid less interest on its debt in the second quarter after it refinanced its borrowings last year.
Gruma shares closed down 1.15 percent at 33.65 pesos in local trading.
$1 = 13.3396 pesos at end June Reporting by Elinor Comlay; Editing by Marguerita Choy