Rowghani, who joined Twitter in March 2010 after nine years with Pixar Animation Studios, will remain at Twitter as a strategic advisor to Chief Executive Dick Costolo. Rowghani’s operating roles will be assumed by other Twitter executives, according to a filing with the Securities and Exchange Commission.

“Goodbye Twitter. It’s been an amazing ride, and I will cherish the memories,” wrote Rowghani in a tweet shortly after the news was disclosed.

The exit comes as Twitter has reported sharp advertising revenue growth, but a troublesome slowdown in user activity. Average monthly active users totaled 255 million at the end of the first quarter, climbing just 5.8% on a sequential basis. Twitter had mostly reported double-digit gains for that key metric throughout much of 2011 and 2012.

Rowghani is leaving Twitter roughly a month after he made a profit of about $9.9 million after selling some Twitter shares on the first day that employees and early investors could do so after the company’s initial public offering in November.

Meanwhile, the elimination of the COO role at Twitter mirrors a trend seen at other companies, as chief executives take greater control of day-to-day operations or delegate control to other executives, squeezing out chief operating officers and presidents. McDonald’s (MCD) and PetSmart (PETM) are among the companies this year that have announced the elimination of the COO position.