Increased costs of borrowing money during an era of record-high interest rates caused profits to decline during the fourth quarter and all of 1979 for Federal National Mortgage Association, the Washington company reported yesterday.

McCormick & Co. reported a banner year, however, and Women's National Bank of Washington said it was profitable during 1979 -- unusual because that was the new bank's first full year of operations.

Federal National Mortgage, known as Fannie Mae, said fourth-quarter profits decline to $37 million (62 cents a share) from $51.1 million (84 cents) during the 1978 period. For all of 1979, earnings fell to $161.7 million ($2.68) from $209 million ($3.47) in the previous year.

The company supports a secondary market for home mortgages and is the nation's largest single owner of mortgages, having bought them from other companies, thus making more money available for lending.

During 1979, Fannie Mae issued commitments to buy residential mortgages totaling $10.2 billion compared with the torrid pace of $19 billion in 1978, the company said. Actual purchases totaled $10.8 billion, down from $12.3 billion, as the housing markets cooled off because of soaring interest rates.

Fannie Mae earned $241 million on its portfolio of mortgages last year compared with a return of $294 million in 1978.

McCormick & Co., a Maryland spice and foods company, reported 1979 earnings of $19.4 million ($1.71 a share) compared with $16.7 million ($1.48) the previous year as sales increased by 14 percent to $457 million. Fourth-quarter profits rose to $10.7 million (95 cents) from $9 million (80 cents).

Chairman Harry Wells attributed the gains to strong sales of seasonings and flavorings as well as continued expansion of industrial, food service and international markets.

National Savings & Trust Co. and Central National Bank of Maryland reported higher profits in 1979, while Women's National announced its first full-year earnings statement.

NS&T, based in Washington, said net income was $3.9 million ($8.62 a share) compared with $3.7 million ($8.06) in 1978. Assets rose to $527.5 million on Dec. 31 from $467.9 million a year earlier.

Central National's earnings rose to $438,975 ($1.98 a share) from $360,071 ($1.69), as assets increased by 10 percent to $57 million and loan volume was up 20 percent to $34 million.

Women's National, the first federally chartered women's bank in the country, said net income in 1979 was $50,240 (50 cents a share) as deposits increased 79 percent over the year to $8.3 million and assets rose by 59 percent to $11 million.

The Washington bank opened in May 1978 and hasn't experienced the operating losses that are common to small, minority-owned financial institutions in their early years of business.

Hotel Investors, a Chevy Chase real estate investment trust that specializes in hotel properties, reported earnings of $1.47 million (87 cents a share in the first quarter of its new fiscal year ended Nov. 30 compared with $680,838 (43 cents) a year earlier. The recent quarter's gains included $390,320 (23 cents) from sale of the Tallahassee Hilton Inn.

Adams Express Co., Baltimore investment firm, reported that net asset value per share rose to $16.14 on Dec. 31 from $14.49 a year ago. Total assets rose to $252 million from $218 million.

Petroleum & Resources Corp., another Baltimore investment firm, said net asset value per share rose to $35.38 from $24.79, while total assets increased to $211 million from $144 million.