The deputy head of the Health Service Executive Pat McLoughlin has tendered his resignation.
Mr McLoughlin is currently the director of the HSE's national hospitals office which oversees 50 acute hospitals in the State.
His resignation was discussed at a HSE board meeting this evening and will continue in his current position until 31st January next.
Mr McLoughlin told RTÉ News that pension entitlements, which had been agreed when he took up his post, were rejected recently by the Department of Finance and he had little option but to leave.
In a statement tonight, HSE chief Professor Brendan Drumm said: "I am disappointed that Mr McLoughlin will be leaving the HSE.
Professor Drumm said: "He has made an outstanding contribution to the development of HSE and particularly with regard to the formation of National Hospitals Office since its inception in January 2005."
"Mr McLoughlin brought his enormous depth of experience and knowledge of the health sector to the post and has been instrumental in introducing a number of important strategic initiatives," he added.