State health officials supplied communities across the Cape and Islands with 1.7 million potassium iodide pills this week — more than enough to protect the thyroids of residents and visitors should a radioactive release occur at the Pilgrim Nuclear Power Station.

Residents are being urged to pick up pills for their families — two per person — and tuck them in their emergency kits.

According to the Nuclear Regulatory Commission, two pills will protect the thyroid for two days. By that time, the agency’s site states, people should have been evacuated or properly sheltered, and therefore out of harm’s way.

The thyroid gland is part of the endocrine system, which controls metabolism. The thyroid cannot differentiate between potassium iodide and the radioactive iodine that’s released in the steam of a failed reactor. Potassium iodide protects the thyroid by filling the gland to the point where it can’t absorb any more iodine for 24 hours.

The new batch of pills, which have a shelf life of seven years, will replace old potassium iodide tablets set to expire this month.

Residents can obtain pills free of charge from their health departments, courtesy of Entergy Corp., Pilgrim’s owner-operator.

The company is required by state law to provide the pills to residents in the 10-mile emergency zone around Pilgrim, as well as to Barnstable, Dukes and Nantucket counties, and Cape Ann, according to Anne Roach, spokeswoman for the Massachusetts Department of Public Health.

Entergy paid a little over 35 cents for each pill, Roach said. That puts the company’s cost to supply the Cape and Islands at just under $600,000.

According to the Centers for Disease Control and Prevention, the younger the person, the more vulnerable the thyroid is to injury from radioactive iodine. All infants, even those who are breast-fed, should be given the recommended dose of potassium iodide in case of a nuclear event, according to the CDC.

Pregnant women are advised to take the pill since all forms of iodine can cross the placenta to the growing fetus.

Those over 40 shouldn’t need the pills unless a massive dose of radiation is on the way, since that group has the lowest chance of developing thyroid cancer.

Past demand for potassium iodide has been low, even though health departments on the Cape have had pills on hand for several years.

“They haven’t been a hot item,” said Dennis Health Director Terence Hayes. “We had 60,000 pills the first time and probably have 59,000 left.”

Brewster resident Rebecca Alvin was one of those who did pick up the pills for her family four years ago, after reading about their availability. She plans to get the new pills now.

“If they’ve got them, I might as well have them,” Alvin said. “Most people I mention it to don’t know towns have the pills.”

Falmouth Health Agent David Carignan said his office is working with the local school district to make the pills available at the schools.

Nancy Taylor, director of pupil personnel services for Falmouth, expects a distribution program to be set up some time this year, but probably not by the time school opens. Parents will be asked to provide permission for their children to receive the pills, Taylor said.

Dennis-Yarmouth Regional School District already has a program in place. Parents have become accustomed to signing the required permission slips at the beginning of every school year.

Yarmouth Health Director Bruce Murphy said he also dropped off a supply this week at St. Pius X School, a Catholic elementary school in South Yarmouth.

Not every school system is interested in stockpiling the potassium iodide. The Nauset Public Schools, which includes Brewster, Eastham, Orleans and Wellfleet, isn’t making any plans.

Ann Caretti, Nauset’s director of student services, said securing pills for the district’s various schools has not been done in the past and isn’t currently under discussion.

Meanwhile, Murphy hopes Yarmouth residents will come to the Health Department to pick up their supply of potassium iodide.

“We encourage them to have the pills as part of their emergency kits, along with Band-Aids and flashlights,” Murphy said. “Those with old pills should throw them out and replace them with new pills.”