Turkey's benchmark stock index dropped 0.74 percent or 688.47 points to open at 91,864.24 points on Thursday.
On Wednesday, Borsa Istanbul's BIST 100 index soared 1.62 percent to close the day at 92,552.71 points with a daily trading volume of 5.4 billion Turkish liras ($1.01 billion).
The U.S. dollar/Turkish lira exchange rate dropped to 5.3080 as of 9.30 a.m. local time (0630GMT), compared with Wednesday's closing rate of 5.3170.
The euro/Turkish lira exchange rate also fell to 6.0580, versus 6.0680 at the last close. One British pound traded for 6.7200 Turkish liras, as the GBP/TRY exchange rate was 6.7330 at market close on Wednesday.
The price of Brent oil dropped to $56.37 per barrel as of 10.00 a.m. local time (0700GMT) Thursday, versus $57.28 at Wednesday close.