In the last few months, as the S&P 500 has shot to new highs and has moved within a few percentage points of the 2,000 level, the sentiment indicators have moved toward bullish extremes.

The most recent indicator to reach such a significant bullish extreme is the CBOE Equity Put/Call ratio. The 21-day moving average for the ratio dropped to 0.5224 last week, the lowest the moving average has been since January 2011.

Because the individual daily readings can vacillate wildly, I don't usually take note of them, and thus the reason for looking more closely at the 21-day moving average.

This past Wednesday was an exception though, as the daily reading was 0.38. That caught my attention. That is the fourth-lowest daily reading in the last four years.

The CBOE Volatility Index (VIX) got in on the action as well by dropping to a low of 10.34 last week. If the market rallies this week, the indicator stands a good chance of dropping below the 10 level for the first time since 2007.

While there aren't any signs that the market is ready to backtrack, the sentiment indicators reaching such bullish extremes gives me cause for concern.

I am not suggesting you should run out and dump all your stock holdings, but I would suggest being on your toes and maybe even taking some defensive actions to protect your portfolio.