Just prior to his rematch with now-former middleweight champion Anderson Silva, Chael Sonnen dramatically declared that he needed to undergo testosterone-replacement therapy, or he would die.

A year later he told California regulators that, if he discontinued the treatment, he would have the hormone levels of a 93-year-old.

A doctor who recently reviewed Sonnen’s medical history would agree the fighter now needs to use prescribed testosterone to compete as a professional athlete. But she is uncertain whether he needed it in the first place.

In a letter written to Sonnen’s management, which was forwarded to the Nevada State Athletic Commission with the fighter’s second request to undergo TRT for UFC 167 this past month, University of Arizona endocrinologist Karen Louise Herbst concluded the fighter meets the criteria for hormone-replacement therapy (TRT). She said he is “likely permanently hypogonadal” because he has used testosterone since 2008.

“It may be that suppression of his gonadal axis for that long may never allow a return to normalcy, and discontinuing his testosterone use at this time would be very disruptive to his career,” she wrote.

But Herbst also expressed reservations about his initial diagnosis of testosterone deficiency. She said that based on “initial data,” it is “not clear that there was a definitive (without a doubt) diagnosis of hypogonadism.”

It is unclear how Herbst came to work with Sonnen. NSAC Executive Director Keith Kizer told MMAjunkie she was referred to the fighter by the UFC and would be reviewing fighters’ medical histories for the promotion in the future. UFC Vice President of Regulatory Affairs Marc Ratner said the UFC had no hand in the process and said Herbst was Sonnen’s doctor.

Sonnen and his management did not respond to requests for comment.

The commission granted Sonnen a therapeutic-use exemption (TUE) for UFC 167, a Nov. 16 pay-per-view event. He lost to former champ Rashad Evans via first-round TKO. He is one of three active UFC fighters granted a TUE for TRT from the commission, along with ex-champs Frank Mir and Dan Henderson.

Hypogonadism is a hormonal deficiency that inhibits the body’s ability to produce testosterone. It is the basis by which doctors prescribe replacement therapy using a synthetic version of the hormone, though experts disagree on who truly needs it.

Although the number of UFC fighters with permission to use testosterone represents a tiny fraction of the promotion’s roster, the practice of granting exemptions for combat-sport athletes remains controversial.

“The whole notion of granting TUEs to young men for hypogonadism is nonsense,” wrote anti-doping expert Don Catlin in an email to MMAjunkie. “Young men do not get hypogonadism. As a member of the committee for the last 20 years, I should mention that we only granted one TUE, and that was for someone who had no testicles.”

Three years ago, the 36-year-old Sonnen introduced hypogonadism and testosterone-replacement therapy to MMA after a post-fight drug test came back with an elevated testosterone-to-epitestosterone (T/E) ratio following his first bout with Silva at UFC 117.

During his appeal of a one-year suspension issued by the California State Athletic Commission, which oversaw the event, Sonnen claimed he was approved to undergo TRT and had disclosed it beforehand to the commission’s executive director.

To bolster his defense, he brought an Oregon-based osteopath to testify to his need for hormone-replacement therapy. Dr. Mark Cznarnecki told the CASC the fighter suffered from “mental fogging” and would be anemic without testosterone.

Czarnecki, who said he was in the process of completing a “hormone-based residency program” with the American Board of Anti-Aging and Regenerative Medicine, clarified that he did not recommend to Sonnen any alternative treatments. Yet he stated the fighter could not safely compete inside the octagon without testosterone.

The CSAC halved Sonnen’s suspension, but later re-suspended him when it found he had made false statements about receiving approval from the NSAC for TRT.

Herbst reviewed Czarnecki’s initial diagnosis and concluded the fighter’s case for deficiency would have been stronger had he been tested differently for hypogonadism. According to her evaluation, Sonnen gave two blood samples on Jan. 11, 2008 – one in the morning and another in the afternoon – that led to a prescription for testosterone.

“A second morning testosterone level that was lower than 300 ng/ml would have been more convincing than a level of testosterone drawn in the afternoon when levels are known to be lower in men,” she stated.

While testifying on Sonnen’s behalf, Czarnecki told the CSAC he performed two blood tests on the fighter, one on Jan. 11 and one four days later. The latter ruled out primary hypogonadism, which results from congenital defects or physical damage to the testes.

That would point to the disease’s secondary form, which occurs when hormone levels decrease as the result of disfunction in the pituitary gland, which tells the body to produce testosterone. While both primary and secondary hypogonadism can cause health problems, doctors disagree on whether the secondary variety is a disease that should be universally treated with hormone-replacement therapy.

Herbst did not identify the type of deficiency suffered by Sonnen but wrote there was no evidence that he had abused testosterone over five years of treatment.

Dr. Jeffrey Brown, a Texas-based endocrinologist who reviewed Sonnen’s paperwork for MMAjunkie, said he takes three blood samples over the course of an hour in the morning and averages the hormone levels of a patient in order to get the most accurate number. Additionally, he gets a full medical history and measures other hormones before deciding the type of deficiency.

Making a diagnosis on incomplete information, he noted, “you can be misled.”

While Brown cautioned that he hadn’t reviewed Sonnen’s full medical history, he agreed with Herbst’s conclusion that the fighter’s initial diagnosis is inconclusive.

“Based on this, if that’s all they went on, in my opinion, that’s not enough (to prescribe testosterone),” he said.

The NSAC’s Kizer, who fielded Sonnen’s application, said the commission requires potential TUE candidates to take two blood tests in the morning, provide medical documentation to support their need for testosterone, and certify they haven’t previously used performance-enhancing drugs. Fighters approved for TRT are advised to maintain testosterone levels in the middle of the range for adult males, which falls approximately between 300 and 1,100 nanograms per deciliter.

Kizer said the commission often receives incomplete information pertaining to medical histories and doesn’t have the benefit of a centralized database of records. He said the ideal situation is to evaluate a fighter who’s never used testosterone so the commission can make sure there aren’t any missing pieces.

In previous talks, he said Sonnen’s reps told him that Czarnecki “didn’t do things as well as he should have” and acknowledged the initial diagnosis could be of questionable validity. But as to whether a misdiagnosis carries any weight in the NSAC’s decision to grant a TUE, the regulator is unsure.

“That’s a good question; I don’t know the answer,” Kizer said. “You’d hate to penalize a patient because their doctor screwed up. I’m not saying that’s the case here or not, but that’s another factor to think about.”

In September 2011, Czarnecki voluntarily retired his Oregon medical license while the state’s medical board investigated him for allegedly failing to diagnose a subdural hematoma in a patient, mismanaging patient’s treatment for an anti-blood clotting drug, and engaging in “substandard medical charting.”

Both before and immediately after UFC 167, the NSAC monitored Sonnen’s testosterone use through multiple blood and urine tests, none of which raised any red flags for abuse. Kizer even speculated that the fighter may have used less testosterone closer to the fight because he was concerned about running afoul with the commission.

“I think should have used more,” he said. “He shouldn’t have been in the 200s; that’s not good for his health. That’s like if your doctor says take two pills a day, you take two pills a week. You’re doing something wrong. But you’re also doing something wrong if you’re taking four pills a day instead of two.

“I understand they want to be cautious. They should be cautious. But you’re a fighter, and you’re in a different category. I don’t want to look like I’m trying to castigate the guy for using too little, but it is something that could be a health problem for him.”

One month from UFC 167, Sonnen’s level of testosterone (233 ng/ml) and other hormones were below the range considered normal (348 ng/ml to 1197 ng/ml) by LabCorp, one of the chief labs used by the NSAC to analyze blood samples. Two weeks out, the levels were in the middle (634 ng/ml), and on fight night, they were low (218 ng/ml), according to tests attached to his TUE application.

Sonnen, according to Herbst’s letter, injects testosterone twice weekly and takes a pill to inhibit the production of female sex hormones.

Brown was more optimistic than Herbst as to whether Sonnen would need the hormone for the rest of his life. He said there are a variety of ways to stimulate the body replace synthetic testosterone with the natural kind.

“It’s possible that it won’t come back, but I don’t agree that it’s necessarily true that it won’t,” he said.

Given his public statements, however, there’s little indication that Sonnen will discontinue his use. Since running afoul of the CSAC, he has received permission from state athletic commissions for TRT in at least five of his most recent bouts.

Prior to his previous bout at UFC Fight Night 26, which he won via first-round submission, Sonnen helped the Massachusetts State Athletic Commission define its criteria for licensing fighters on prescribed testosterone.

Sonnen (29-13-1 MMA, 7-6 UFC) is next scheduled to coach “The Ultimate Fighter: Brazil 3” opposite rival Wanderlei Silva (35-12-1 MMA, 5-7 UFC) and likely will face off with “The Axe Murderer” at light heavyweight in summer 2014.

Brown said he’s seen an upsurge in men who come into his office seeking replacement therapy. Some already are on testosterone or have previously used performance-enhancing drugs that sap their body’s natural ability to produce the hormone.

“It increases my business, because what happens is people get placed on testosterone, and they bring their testosterone levels up, but they don’t feel any better,” he said. “That’s because wasn’t the cause of what they felt like anyway.

“There are all these causes that can cause it, and the treatment is not giving testosterone. The treatment would be finding the secondary cause.”