"Investor relations (IR) is a strategic management responsibility that is capable of integrating finance, communication, marketing and securities law compliance to enable the most effective two-way communication between a company, the financial community, and other constituencies, which ultimately contributes to a company's securities achieving fair valuation."
This is a Wikipedia definition and naturally it doesn't have startups in mind. No startup we know has an "investor relations" function, nor do we think it is justified at early stage company. That said, to optimize the success of the company, the CEO must adopt an "investor relations" mindset early on, and adopt tools and processes that support it.