UPDATE 2-GN Store Nord swings to profit but sales disappoint

* Q3 sales down 20 percent, vs forecast 10 percent fall

* Q3 EBITA 45 million Danish crowns, vs forecast 41 million

* Trims 2009 sales forecast, repeats EBITA guidance

* Says hearing aid unit lost market share in Q3

* Shares down 7.9 percent

(Adds detail, quotes, updates share price)

By John Acher

COPENHAGEN, Nov 11 (Reuters) - Danish hearing aid and headset maker GN Store Nord (GN.CO) swung to a third-quarter core profit thanks to cost cutting, but sales shrank more than expected amid fierce competition.

GN Store Nord repeated full-year earnings guidance but lowered its sales guidance, leading its shares down 7.9 percent to 25.50 crowns by 1045 GMT on Wednesday, underperforming a 0.5 percent rise in the Copenhagen bourse blue-chip index .

Its July-September earnings before interest, tax and amortisation (EBITA) came to 45 million Danish crowns ($9.1 million), against a forecast of a 41 million profit in a Reuters poll and after a 27 million loss a year ago.

Sales fell 20 percent, more than the company had expected, to 1.11 billion crowns, below a forecast for 1.25 billion.

Nordea said in a note the sales were disappointing and the numbers suggested GN was losing market share to its biggest rival, Swiss-based Sonova (SOON.VX).

GN Store Nord said it now expected 2009 revenue of around 4.7 billion crowns versus an earlier forecast for around 5 billion. It kept its EBITA forecast steady at 65 million crowns.

TOUGH COMPETITION...

GN, whose hearing aid unit also competes with Danish company William Demant (WDH.CO) and German conglomerate Siemens (SIEGn.DE), said the total U.S. market grew 9 percent thanks to growth in sales to veterans.