What are the parathyroid glands and what does PTH do?
The parathyroid glands are four small glands, each about the size of a grain of rice, sitting behind the thyroid in the neck. Despite the shared location, they have nothing to do with thyroid hormone: their single job is to keep blood calcium within a narrow range using parathyroid hormone (PTH).
In primary hyperparathyroidism, a small benign growth called a parathyroid adenoma keeps producing PTH even though calcium is already high. This is the most common cause of persistently raised calcium and is diagnosed on blood tests, not on imaging.
Symptoms and findings that raise suspicion
These symptoms are non-specific and have many other causes, so the diagnosis rests on the blood results and the overall clinical picture rather than on symptoms alone.
- A raised calcium level found on a routine blood test, often repeated over months.
- Recurrent or unexplained kidney stones.
- Reduced bone density or osteoporosis on a DEXA scan.
- Fatigue, low mood, poor concentration or muscle weakness.
- Bone and joint aches alongside a high calcium level.
Tests and localisation imaging
Imaging does not make the diagnosis. It is used after the biochemistry confirms hyperparathyroidism, to show which gland is responsible and to plan a focused operation.
- Serum calcium, with ionised calcium where needed.
- Parathyroid hormone (PTH), vitamin D and kidney function.
- Urinary calcium in selected cases, to exclude other causes of high calcium.
- DEXA bone density scan to assess the effect on the skeleton.
- Neck ultrasound, and a sestamibi scan when clinically appropriate, to localise the overactive gland before surgery.
When monitoring is enough and when surgery is considered
Not every case needs an operation. When calcium is only mildly raised, there are no symptoms, and kidney function and bone density are satisfactory, regular monitoring with correction of vitamin D deficiency and good hydration is a reasonable plan.
Parathyroidectomy is usually discussed when calcium is clearly elevated, when kidney stones or reduced bone density are linked to the condition, when symptoms affect daily life, or in younger patients with a confirmed diagnosis. The aim is to remove only the overactive gland.
Calcium after parathyroid surgery
Calcium normally falls once the overactive gland is removed and is checked with blood tests over the first days. Some patients need calcium or vitamin D supplements for a period while the remaining glands and the bones adjust. Follow-up confirms that calcium and PTH have settled.
