Abnormal Conditions/ Hyperparathyroidism
In these cases, there is an abnormal accumulation of parathyroid cells that do not behave in a structured and normal pattern and produce excess amounts of parathyroid hormone (PTH). This over-production is autonomous, meaning that it happens even of the calcium in the blood is already at normal levels. As a result the overproduction of PTH will eventually result in an increase of blood calcium.
- Primary hyperparathyroidism occurs when the normal negative feedback control of serum is calcium is disrupted due to an excess production of PTH.
- In secondary hyperparathyroidism there is a disruption in mineral homeostasis mainly due to renal disease or vitamin d deficiency.
- Tertiary hyperparathyroidism is encountered whenever the hyperplastic glands begin an autonomous function secondary to prolonged stimulation.
Primary hyperparathyroidism (PHPT) is caused by an excess production and secretion of PTH. It affects up to 0.3% of the population with an almost 3:1 female to male ratio. The peak age at presentation is 56 to 60 years and 79% of all cases occur over the age of 46 years. The prevalence of PHPT in women under the age of 40 is thought to be less than 40/100,000 with 8% of all cases of PHPT occurring in women of child-bearing age.
Increased PTH production leads to hypercalcaemia via increased gastrointestinal absorption of calcium, increased production of vitamin D3 and reduced renal calcium clearance. PHPT is characterized by increased parathyroid cell proliferation and PTH secretion which is independent of calcium levels.
Primary hyperparathyroidism can be caused most frequently by a single benign tumour of the parathyroid glands – an adenoma, a double adenoma or by hyperplasia of all four glands.
- Single chief cell adenomas are the most common cause of PHPT and account for the majority of cases (87-90%). Most adenomas occur sporadically and affect only a single gland.
- However double adenomas account for approximately 3-8% of the cases.
- Four-gland hyperplasia typically refers to the enlargement of all four parathyroid glands and occurs in 3-5% of patients with PHPT . This is more typical of familial hyperparathyroidism but may also be found in sporadic cases. Hyperplasia is often associated with the autosomal dominant Multiple Endocrine Neoplasia (MEN) syndromes.
Parathyroid carcinoma is responsible for less than 1% of all parathyroid hormone dependent hypercalcaemia. It is characterized by severe hypercalcaemia and often a palpable cervical mass. Parathyroid carcinoma can invade neighboring organs such as thyroid and neighboring vessels. Local recurrence and/or distant metastases to lung, liver or bone are also diagnostic of malignancy. With the current technology, it is impossible to accurately predict pre-operatively the presence of a parathyroid cancer, however there are certain features/findings that might point to this diagnosis.
Hyperparathyroidism and genetic conditions
In patients with Multiple Endocrine Neoplasia type 1 (MEN1), there is a high prevalence of PHPT associated with pituitary and pancreatic neuroendocrine tumours. Hyperparathyroidism can also occur in Multiple Endocrine Neoplasia type 2 (MEN2A), but with less frequency. MEN 2A is characterized by medullary thyroid cancer, pheochromocytoma, and PHPT. However, it almost never occurs in Multiple Endocrine Neoplasia type 2B (MEN2B).
Clinical Manifestations of PHPT
Patients with PHPT may present with the “classic” symptoms: kidney stones, painful bones, abdominal groans, psychic overtones. However with the widespread use of automated blood analysers in the early 1970s, the “typical” patient with PHPT, is now more likely to be minimally symptomatic or even asymptomatic. Some patients are completely asymptomatic even with very high levels of calcium in their blood.
The majority of patients however present vague symptomatology including:
Bone & joint pain
Radiologic Investigations for PHPT
The success rate of curing a patient from PHPT for Mr Christakis is the same independent of whether your scans are positive or negative. That means that even if your scans have not picked up the culprit parathyroid, Mr Christakis can find it and remove it.
Mr Christakis will have a consultation with you and determine which radiologic investigation you need in order to localise the abnormal parathyroid tumour(s). The available options an Ultrasound of the neck, a nuclear Sestamibi scan and a 4D-CT scan of the neck.
Sometimes the scans are completely negative. Furthermore, they might pick up a thyroid nodule or a lymph node and call it a parathyroid tumour. Or there might be a very large parathyroid tumour and the scans have completely missed it. Mr Christakis routinely operates on patients who have completely negative scans and he is able to cure them with the same high success rates.
Imaging has no utility in confirming or excluding the diagnosis of PHPT, hence the presence of negative scans does not mean that you should not have a parathyroid operation.