Investors thumped Bank of Queensland's share price on Monday after the company flagged that it was set to report an interim bottom line at least 6.5 per cent below its first half result last year.BoQ, which balances its first half operations at the end of this month, expects its interim net profit to come within the range of A$165 million and $170 million.That's at least $12 million down on the 2018 first half profit of $182 million.The BoQ update is the latest in a stream of disclosures in the last month from major and regional banks that each point to a deterioration in interest margins, lending activity and fee income.BoQ attributed most of the expected decline in its upcoming six-month result to run-off in fee revenue."This is due to continued downward pressure across fee, trading, insurance and other income lines," the bank told the ASX.While the bank said that net interest income was expected to be in line with the $475 million reported in the corresponding period last year, it revealed that its net interest margin could fall by as much as four basis points to 1.93 per cent."The reduction in NIM is primarily attributable to continuing funding cost pressures (including the elevated bank bill swap rate) and price competition for new loans," the bank said."Recurring operating expenses have been largely in line with expectations, however some non-recurring costs have negatively impacted the half year result." The bank's management is also cautious about the prospects of recovery in performance in the second half amid expectations of higher regulatory costs flowing from the recommendations of the Hayne royal commission."Looking forward to the second half, market conditions are expected to remain challenging. We expect regulatory costs to increase as BOQ adapts to changes in regulatory requirements and expectations, including the impacts of the Royal Commission," the bank said.The trading update disappointed the market, which forced several analysts to cut their earnings estimates for the company.The new earnings guidance forced GoldmanSachs to lower its forecast for the interim profit by 8 per cent.We note that relative to our current first half 2019 cash earnings forecast of $183 million, the mid-point of BOQ's 1H19 guidance range would represent 8 per cent downside to our estimate," Goldman Sachs told clients in a report."Our current full year 2019 cash earnings forecast is $363 million.  We are Sell rated."The bank's share price copped a big hit, closing down 63 cents or 6.3 per cent to $9.32.Trading in the stock was heavy, with the number of shares changing hands more than three times the daily average.