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What is ADH1?

Autosomal dominant hypocalcemia type 1 (ADH1) is a rare genetic condition and a common cause of nonsurgical hypoparathyroidism (HypoPT).1

It is an inherited endocrine disorder characterized by these biochemical findings2:

  • Decreased parathyroid hormone (PTH) secretion
  • Low serum calcium concentration (hypocalcemia)
  • Increased urinary calcium excretion (hypercalciuria)
Circle icon with forest green background featuring 4 people icons in gray and 1 in yellow with text: ADH1 affects up to 1 in 25,000 people
Icon in forest green of human body featuring gold thyroid and kidneys, and grey circle with gold process in chest

ADH1 is a distinct form of hypoparathyroidism

Hypoparathyroidism can result from surgical or nonsurgical etiologies, which include genetic disorders.1 ADH1 is a genetic form of nonsurgical hypoparathyroidism caused by gain‑of‑function variants in the calcium-sensing receptor gene (CASR), of which over 100 are known.2

Variants in the calcium-sensing receptor (CaSR) are responsible for1,2:

  • Reduced PTH secretion
  • Reduced renal calcium reabsorption

The mechanism of disease in ADH1 is distinct from that of other forms of hypoparathyroidism because of the critical role of the CaSR in both the parathyroid glands and kidneys.2,3

ADH1 symptoms and impact on patients2

A common sign of ADH1 is low serum calcium, which results in symptoms including tetany, muscle cramps, and spasms. In more severe cases, seizures, laryngospasms, and cardiac arrhythmias are experienced. Conventional treatment (calcium and active vitamin D supplementation) can lead to kidney calcification, kidney stones, and even kidney failure.

Physical symptoms of ADH1

  • Muscle cramps and spasms (tetany)
  • Seizures
  • Laryngospasms
  • Heart rhythm disorders

Symptoms can be mild or severe4

While pediatric cases often present with severe symptoms, like seizures and tetany, adult symptoms can be less obvious and patients don’t associate their symptoms with hypocalcemia. A detailed review of symptoms and family history can help inform diagnosis.

Long-term complications*

  • Kidney calcification (nephrocalcinosis)
  • Kidney stones (nephrolithiasis)
  • Kidney failure

*Result of prolonged conventional treatment with calcium supplements and active vitamin D analogues.

See the wide-ranging effects of HypoPT on the body5,6

Select each body system to learn more

Illustration of the human body showing the organ systems affected by hypoparathyroidism
Collection of icons include blue cloud with raindrop, human head with puzzle piece and heart rhythm and triangle with exclamation point

The hidden burden of ADH15

People living with hypoparathyroidism, including ADH1, may experience these quality-of-life challenges:

  • Fatigue
  • Depression
  • Cognitive impairment
  • Anxiety
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Some people with ADH1 never learn of the underlying genetic cause of their condition and may never receive optimal disease management.

What causes ADH1?

Video overview: Understanding ADH1

Gain‑of‑function variants in the CASR gene are the root cause of ADH15

These CASR variants cause the CaSR to be overly sensitive to calcium, thereby causing it to detect low serum calcium concentration as "normal." This leads to decreased PTH secretion from the parathyroid glands and decreased calcium reabsorption in the kidney. The result is:

  • Low serum calcium concentration (hypocalcemia) and high (hypercalciuria) or inappropriately normal urine calcium concentration
black header 3 circles featuring blood system, parathyroid and kidneys.
gold header with 3 circles featuring blood system in gold, parathyroid with red dots, and kidneys in gold

Ca=Calcium.

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Genetic testing is recommended for patients with nonsurgical or idiopathic hypoparathyroidism.

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References: 1. Mannstadt M, Cianferotti L, Gafni RI, et al. Hypoparathyroidism: genetics and diagnosis. J Bone Miner Res. 2022;37(12):2615-2629. 2. Roszko KL, Stapleton Smith LM, Sridhar AV, et al. Autosomal dominant hypocalcemia type 1: a systematic review. J Bone Miner Res. 2022;37(10):1926-1935. 3. Roszko KL, Bi RD, Mannstadt M. Autosomal dominant hypocalcemia (hypoparathyroidism) types 1 and 2. Front Physiol. 2016;7:458. 4. Khan AA, Ali DS, Bilezikian JP, et al. Best practice recommendations for the diagnosis and management of hypoparathyroidism. Metabolism. 2025;171:156335. 5. Hypoparathyroidism Association. Fast Facts: Hypoparathyroidism. Accessed August 17, 2026. https://www.hypopara.org/patients/symptoms-treatment. 6. Roszko KL, Stapleton Smith LM, Sridhar AV, et al. Autosomal dominant hypocalcemia type 1: a systematic review. J Bone Miner Res. 2022;37(10):1926-1935. doi:10.1002/jbmr.4659