The United Nations System consists of the central political organization, its 11 subsidiary entities, 15 autonomous Specialized Agencies and two related bodies, the International Atomic Energy Agency and the World Trade Organization.
They are rather fitfully coordinated by twice a year meetings of a Chief Executives Board (CEB) under the chairmanship of the UN Secretary-General.
I've just listed the (21) men and (8) women who make up the CEB and it makes interesting reading. The women are outnumbered but they run the largest and most influential agencies, including the IMF, the World Food Program (world's largest aid agency), the World Health Organization and UNDP (world's largest technical assistance agency).
The listing has links to the biographical pages of the relevant agencies