LEXINGTON, Ky. - Thoroughbred great John Henry, the two-time Horse of the Year who earned more than $6.5 million, was euthanized Monday. He was 32.

Kentucky Horse Park spokeswoman Lisa Jackson said the Hall of Famer’s health had declined over the weekend. He had lost considerable body mass and was in kidney failure, she said.

“The next step would have been so hard on him,” she said. “It wouldn’t have been comfortable. ... It just wouldn’t have been fair to the horse.”

Foaled March 9, 1975, and an average runner early in his career, John Henry was the highest earning thoroughbred in history when he was retired to the park in 1985.

The gelded son of Old Bob Bowers out of Once Double won four Grade I races and Horse of the Year honors at age 6 and 9 and collected seven Eclipse awards from 1980 through 1984.

John Henry earned 39 victories, 15 seconds and nine thirds in 83 starts and earned $6,597,947. He was inducted into thoroughbred racing’s Hall of Fame in 1990.

“What can I say about the legendary John Henry that has not already been said,” Chris McCarron, who rode John Henry in 14 of his last races, said in a statement from the park.

“Everywhere he raced, his presence doubled the size of a normal race track crowd. He did so much for racing, even after he retired, that he will be impossible to replace. He will be sorely missed but forever in our hearts.”

Foaled at Golden Chance Farms in Kentucky in 1975, John Henry was considered “small” and “bad-tempered.” He was sold at the January mixed sale at Keeneland for $1,100.

He soon became known more for his disposition than his racing ability, often tearing buckets and tubs of the wall of his stall and stomping them flat.

Harold Snowden of Lexington bought John Henry for $2,200 in 1977. Snowden chose to geld John Henry hoping it would calm him and allow him to focus on racing.

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Eventually, New Yorker Sam Rubin and his wife, Dorothy, bought him for $25,000 sight unseen over the phone. Under trainer Bob Donato, John Henry won six of 19 starts as a 3-year-old. As a 4-year-old, he won four of 11 races for trainer Lefty Nickerson.

The following year, John Henry was sent to work with trainer Ron McAnally in California and his career blossomed.

He won six consecutive stakes races as a 5-year-old, including four Grade I races — the San Luis Rey Stakes, the San Juan Capistrano Invitational, the Hollywood Invitational and the Oak Tree Invitational.

That year also saw him claim his first of seven Eclipse awards as the nation’s champion turf horse. He finished the 1980 campaign with eight victories and three seconds in 12 starts.

John Henry’s remarkable run continued for the next four years as he won 18 of 30 starts. In 1981, he won eight of 10 starts and was named champion grass horse, champion older horse and horse of the year.

As a 9-year-old, John Henry won four straight stakes races, claimed $2.3 million in earnings and again was named champion grass horse and horse of the year.

He won what proved to be his last race, the Ballantine’s Scotch Classic at the Meadowlands on Oct. 13, 1984. John Henry was scheduled to run in the inaugural Breeders’ Cup Turf Classic that year, but strained a ligament. Rubin planned to race John Henry as a 10-year-old, but changed his mind in July 1985, after the horse injured a leg during training.

“If he’d have broken down on the race track, I couldn’t have lived with it,” Rubin said at the time.

Tom Levinson, Rubin’s stepson, said in the statement that his mother and Rubin “loved sharing John’s victories with his adoring fans and we appreciate their devotion even to this sad day. ... We are sure that if Sam Rubin were here today, he and my mother Dorothy would agree that their wish would be for John Henry to be remembered as the mighty, cantankerous champion we all loved.”

Although he never won a Triple Crown race, John Henry was loved because he was a fighter who would battle to win at any cost.

“John Henry was a testament to the fact that a horse’s value is far greater than the sum of his pedigree, conformation, sales price and race record,” Kentucky Horse Park executive director John Nicholson said in a statement.