Analysts with Compass Point Research & Trading held Fifth Third Bancorp ($18.25 0.23%) at a neutral rating after determining the bank's recent loan growth may not be sustainable.

Fifth-Third's mortgage banking originations grew from $5.8 billion to $7 billion in the fourth quarter as the company reported an increase in non-interest income from an increase in residential mortgage origination volumes.

"The outsized loan growth was driven by higher C&I and residential mortgages held-for-sale balances," Compass Point reported.

However, analysts with the research firm said gain-on-sale margins could contract to 2010-2011 levels on a revised HARP program or changes to reps and warrants policies, GSE g-fee increases and declining origination volumes.

"Most regionals banks are recording less than 2% growth in their overall loan balance from the previous quarter," said Compass Point. "We believe FITB's outsized growth was due to the timing of holding residential mortgages held-for-sale on balance sheet and increased commercial line utilization for tax purposes. We expect both drivers of loan growth for FITB to have a difficult time repeating the 4Q12 result without a pickup in economic activity."

Fifth Third Bancorp's fourth-quarter earnings rose 27% as the regional bank wrote off fewer loans and continued to grow its commercial and industrial loan business. The bank reported a net income of $390 million, of $0.43 per diluted share, compared to $354 million, or $0.38 per diluted share, in the third quarter.