US President Barack Obama turned 50 Thursday, marking the milestone in private in a White House with little to celebrate as poor economic news cast a cloud over his reelection prospects.Senior political staff raised a glass to Obama before he joined his family and close friends at a party that included his daughter Malia, 13, back from summer camp for her dad\'s special day. But even a riotous party would be unlikely to drown out the cares of office for Obama, nursing political wounds from a debt clash with Republicans and confronting new fears that the sickly US economy is getting worse.The president did not appear in public on his birthday, a day in which economic fears of ordinary Americans were exacerbated by a stock market plunge that saw the Dow Jones Industrial Average tumble 4.3 percent.But First Lady Michelle Obama told supporters in an email that her husband was doing everything he could to help them through tough times.\"Every day, I see Barack make choices he knows will affect every American family. That\'s no small task for anyone -- and more proof that he\'s earning every last one of those gray hairs,\" she wrote.The message directed recipients to Obama\'s 2012 campaign website, as part of an effort to rebuild the formidable grassroots operation that helped power him to the White House in 2008.Obama opened his celebrations in Chicago on Wednesday night, as supporters serenaded him with a chorus of \"Happy Birthday,\" and he let off steam at several political fundraisers. \"I could not have a better early birthday present than spending tonight with all of you,\" he said, joking that he was expecting an email from a senior citizens group telling him to lobby President Obama over health care for the elderly. Obama, who has said his crisis-strewn two-and-a-half years in office have left him with bags under the eyes, mulled on the prospect of turning 50 in a recent interview. \"Obviously, I\'ve gotten a little grayer since I took this job but otherwise, I feel pretty good,\" he told National Public Radio, adding that his wife was helping him get over the hurdle of hitting the half-century mark. \"Michelle, you know, says that... she still thinks I\'m... cute, you know. And I guess that\'s -- that\'s all that matters, isn\'t it?\" One of the first with birthday wishes was Russian President Dmitry Medvedev, who called Obama on Wednesday to also discuss Moscow\'s pending entry into the World Trade Organization. Obama, born in Hawaii in 1961, marks his birthday at a time when his job approval ratings have dipped to 42 percent after a showdown with Republicans over raising US government borrowing that many commentators scored as a defeat for the White House. He is also haunted by a stagnant economy and high unemployment that pose warning signs for his effort to convince voters in November 2012 that he deserves a second term.  Birthday celebrations could end abruptly on Friday morning with the scheduled release of latest jobs data from the US Labor Department expected to show no easing of the 9.2 percent unemployment rate.Republicans were hardly lining up to offer congratulations to the man they want to turf out of the White House in the 2012 election.A mock up of an e-card sent to reporters pictured the president wearing a superimposed party hat outside the White House.\"Another year older, if only you were another year wiser, then there might be something to celebrate,\" the card said, listing 50 unflattering statistics of current American life, starting with the $14.3 trillion national debt.