HADLEY — Hadley Town Administrator Carolyn Brennan is poised to retire in December after more than four years serving in the role.

Brennan last week submitted a retirement letter to the board, citing “recent medical issues” as a factor in departing.

In an email, Brennan wrote that retirement is a “difficult decision” but that the Select Board has been very supportive.

While her retirement is effective Dec. 9, Brennan will be taking sick time until that point, which she and the Select Board jointly determined would be best for herself and the town.

The Select Board agenda for Wednesday’s meeting notes, under “employee appointments, resignation and retirements,” that Brennan has submitted a letter of retirement.

In addition, as an action item on the agenda, the board anticipates appointing Police Chief Michael Mason to be the interim town administrator.

Select Board Chairwoman Molly Keegan confirmed Tuesday that the board would have more discussion about Brennan’s decision at the upcoming meeting, adding that the board hasn’t been able to have any conversations about the future direction for the town.

The board was scheduled to meet in executive sessions last Wednesday and Thursday for “strategy sessions in preparation for negotiations with nonunion personnel” and “contract negotiations with nonunion personnel — town administrator,” though the second closed-door session was canceled.

Brennan began her tenure in Hadley as the town’s third permanent town administrator in September 2020, succeeding David Nixon, who was in the position for 15 years.

Brennan’s pervious ties to Hadley included her time as an undergraduate at the University of Massachusetts and work at the former Shady Lawn Rest Home.

Brennan was also the director of the East Longmeadow Council on Aging before coming to Hadley, and chaired Wilbraham’s Select Board.

Over the winter, Brennan was the runner-up to become Palmer’s town manager, a position that she sought at the time so she could work closer to her home and to shave off eight hours of commuting weekly to Hadley.

In April 2023, the Select Board, following a positive performance review, ratified a three-year contract with Brennan that paid her $114,572 starting July 1, 2023, with the annual base pay to increase by 15% effective both July 1, 2024 and July 1, 2025, meaning her salary would go to $131,758 and then $151,251. The new contract also had provisions for merit salary adjustments at the Select Board’s discretion.

Much of Brennan’s time has been on project management, including working on the Department of Public Works building project, oversight of personnel, as well as being part of Hadley’s financial team.

Brennan has also been involved in writing a description for a combined assistant town administrator and human resources director position to give her more support, following the resignation of Troy Brin, the third permanent human resources director.

Hadley officials have been discussing a change in government, including moving to a strong town administrator, which if Town Meeting approved, would mean that person having more responsibility over hiring, firing and disciplining town employees, as well as over contracts and collective bargaining.