The Race to Bring Back a Hormone Most People Have Never Heard Of

You probably know that proteins are made of amino acids. Peptides are short chains of those same amino acids — too short to be a full protein, but long enough to do real work in the body.

Some peptides are hormones that signal cells what to do. Insulin is a peptide. So is parathyroid hormone, or PTH for short, which is the focus of this article.

For most of medical history, peptides made bad drugs. They are fragile. Stomach acid breaks them apart before they reach your blood, which is why insulin and almost every other peptide hormone has to be injected. Modern chemistry has been slowly changing that, and the story below is one of the cleanest examples of how.

Your thyroid is the well-known gland in your neck that controls metabolism. Behind it sit four tiny lumps about the size of rice grains called the parathyroid glands. Different name, different job. They make PTH, and PTH has one main mission: keep the calcium level in your blood steady.

Calcium matters more than most people realize. Your nerves need it to send signals, your muscles need it to contract, and your heart needs it to beat in rhythm. If blood calcium drops too low, you can get muscle cramps, tingling around the lips and fingers, anxiety, brain fog, and in severe cases, seizures.

PTH does its job through three organs. The kidneys hold onto calcium under its direction instead of flushing it out in urine. The gut absorbs more calcium from food. And bone cells release stored calcium when blood levels run low, while also coordinating new bone formation. Take PTH out of the picture and the whole system stalls.

Sometimes the parathyroid glands stop working. The most common cause is accidental damage during thyroid surgery, when a surgeon removes a thyroid tumor or treats thyroid cancer and the tiny parathyroids next door get bruised or removed by mistake. Other causes include autoimmune attacks and rare genetic conditions.

When the loss of PTH lasts forever, the condition is called chronic hypoparathyroidism. Roughly 60,000 to 100,000 people in the United States live with it.

For decades, the only treatment for chronic hypoparathyroidism has been to swallow large doses of calcium plus active vitamin D, often several times a day. That keeps blood calcium just high enough to avoid the worst symptoms. But it does not fix the actual problem.

PTH does more than push calcium up in the blood. Without it, the kidneys dump calcium into urine even as patients swallow more by mouth. Over years, that can damage the kidneys themselves. Bones lose their normal cycle of breakdown and rebuilding. Patients often describe a slow exhaustion and mental cloudiness that calcium pills never reach.

For a few years, patients did have a real PTH replacement. The drug was called Natpara, sold by Takeda, and it was a daily injection of full synthetic PTH(1-84). It worked, but Takeda recalled Natpara in September 2019 after problems with the rubber septum on the delivery cartridge, and the company permanently discontinued production in 2024. That left people with chronic hypoparathyroidism in the same place they had been for the previous forty years.

The Danish company Ascendis Pharma built a drug called TransCon PTH (medical name palopegteriparatide) using a clever chemistry trick. They start with the normal PTH peptide and chemically attach it to a tiny carrier molecule. When the drug is injected, the carrier slowly releases PTH into the bloodstream over 24 hours, mimicking how a working parathyroid gland naturally pulses the hormone in small steady doses.

Ascendis ran a Phase 2 trial called PaTH Forward in adults with chronic hypoparathyroidism. On June 11, 2026, the company reported five-year follow-up data: 82% of patients had completely stopped taking active vitamin D and were on less than 600 milligrams of calcium per day at week 266. Ninety-five percent of patients who started the trial finished the full five years.

The biology held up too. Patients' urine calcium normalized, their bone mineral density stayed stable, and their quality-of-life scores rose above where they started and stayed there. In plain language: TransCon PTH did the job a working parathyroid gland would do.

The American company MBX Biosciences (Nasdaq: MBX) took a different route. Instead of trying to mimic the body's natural pulsing of PTH, MBX engineered a longer-acting modified PTH peptide called canvuparatide that lasts in the body long enough to work with just one injection per week.

On June 12, 2026, MBX reported full Phase 2 results from a trial named Avail. At week 12, 63% of patients on canvuparatide met the treatment goal of normal blood calcium without active vitamin D and on less than 600 milligrams of supplemental calcium per day, versus 31% on placebo. In the one-year follow-up study, the response rate held at 57%, and 90% of patients stayed enrolled the full year.

The case for once-weekly dosing is convenience. A weekly injection fits the routine patients already follow for other long-acting drugs, including the GLP-1 weight-loss medicines that have become common. MBX plans to start the registrational Phase 3 trial, the larger trial needed for FDA approval, in the third quarter of 2026.

The most ambitious approach belongs to Entera Bio (Nasdaq: ENTX), a small Israeli company with a delivery platform called N-Tab. The N-Tab system uses chemical wrappers and absorption helpers to protect peptides from stomach acid long enough for them to cross the gut wall and reach the bloodstream intact. If the platform works, the result is a peptide hormone you can swallow as a regular tablet.

Entera's lead drug is EB613, an oral version of teriparatide, the synthetic fragment of PTH already sold as an injection for osteoporosis under the brand name Forteo. Entera is testing oral EB613 first for postmenopausal osteoporosis (bone weakening that affects women after menopause) and is developing a separate oral PTH(1-34) product called EB612 specifically for hypoparathyroidism.

On June 13, 2026, Entera presented single-tablet pharmacokinetic data for EB613 as a late-breaking oral presentation at ENDO 2026 in Chicago. The Phase 3 trial in 750 postmenopausal women is scheduled to start in late 2026, with topline results expected in the second half of 2028. The hypoparathyroidism program (EB612) is at an earlier stage, but the same N-Tab platform applies.

If Entera succeeds, the same delivery technology could carry oral peptide hormones into dozens of other diseases where injection has been the only option. That is the bigger reason this approach matters, even though EB613's first target is osteoporosis rather than the disease the other two companies are racing for.

The reason all three of these readouts landed within a single week is the timing of ENDO 2026, the Endocrine Society's annual meeting, held in Chicago June 13 through 16. Endocrinology is the medical specialty that studies hormones, and ENDO is the field's biggest annual gathering. Hypoparathyroidism is one of the standard topics. So is osteoporosis. So is the chemistry of PTH.

Drug companies time their data releases to land at ENDO when they can. The result this year was three companies, three different bets on what PTH replacement therapy should look like, presenting in the same hall over the same four days.

Ascendis bet on physiology. Build a drug that mimics what a working parathyroid gland would do: daily injection, slow release, 24-hour coverage.

MBX is making a different trade. Their molecule is less natural in its profile, and the deal is convenience: one shot per week instead of one per day. For people whose daily-injection fatigue is real, that can be the difference between sticking with treatment and quitting.

Entera is betting on the route of delivery. A patient who can swallow a pill instead of taking any shot has a different experience of treatment, and the same platform could carry other peptide drugs along with it.

Whichever approach wins, the practical change is real. Chronic hypoparathyroidism has been an under-treated disease for two generations. Patients have been told to take more calcium pills and hope. Now, for the first time since Natpara left the market, actual PTH replacement is back, with three different versions racing toward approval.

Ascendis is the furthest along, with five-year Phase 2 data in hand and the regulatory filings being prepared for a broader patient population.

Right behind is MBX, whose Phase 3 trial starts in the third quarter of 2026. For a rare disease like hypoparathyroidism, where the patient population is small, approval typically takes two to three years from there.

Entera's path is the longest. EB613 needs its own Phase 3 (already on the calendar) and full topline data in late 2028. But the platform potential runs far beyond a single drug. If Entera proves that oral PTH peptides work in osteoporosis, the same chemistry could be applied to canvuparatide, TransCon PTH, and the rest of the peptide drugs that are currently injection-only.

For middle and high school readers paying attention to medicine, hypoparathyroidism is a story worth knowing about, even if you have never heard of the disease. It does not get covered by mainstream news. The patients are too few, the symptoms are too easy to mistake for stress or anxiety, and the treatment field was frozen for so long that nobody noticed when it started moving again. This June, three companies set the entire field in motion. Which one wins, and how fast they can scale, will shape what tens of thousands of patients live with for the next decade.