We have encountered many such patients in the clinic: some are young in age, with multiple bone pains all over the body, unable to bear weight, walking with difficulty, or even unable to get up or turn over, with a lot of various tests done, but the cause cannot be found; some have recurrent, active urinary stones, or even impaired kidney function, repeatedly treated many times and still recurring, bringing countless troubles and pains to the patients; some are young in age, with fragile bones, prone to fractures, as if “glass man”; and unexplained hypercalcemia, osteoporosis, muscle weakness of limbs, muscle pain, diffuse calcification of lungs, etc. The ultimate cause can be the tiny parathyroid glands that are easily ignored by us. Conditions such as the above are not uncommon in clinical practice, but often patients are bounced around to multiple hospitals before parathyroid lesions are considered, making us look at the tiny parathyroid glands differently.
First of all, let’s get to know the parathyroid glands in our body. The normal parathyroid glands can have a variety of shapes, such as ovals, rods, balls, discs, or blades. The average size of the parathyroid glands is 5 x 3 x 1mm, with a minimum of 2 x 2 x 1mm and a maximum of 12 x 2 x 1mm, and an average weight of 35-40 mg. The average person has four parathyroid glands, with two glands on the left and two on the right. The superior parathyroid glands are generally found behind the lateral lobe of the thyroid gland at the level of the cricoid cartilage and near the laryngeal nerve where the recurrent laryngeal nerve enters the larynx. The inferior parathyroid gland is located behind the lateral lobe of the thyroid gland at the level of the lateral centile, near the level where the inferior thyroid artery intersects with the recurrent laryngeal nerve. In a small number of people, there are only 3 parathyroid glands (13%, 2 glands on one side are combined) or as many as 5 parathyroid glands (6%, the extra one is often in the mediastinum).
The parathyroid glands secrete thyroxine (PTH). The parathyroid glands have the following roles.
1. Promote calcium reabsorption by the proximal renal tubule, resulting in a decrease in urinary calcium and an increase in blood calcium.
2. Inhibit the absorption of phosphorus by the proximal renal tubule, resulting in an increase in urinary phosphorus and a decrease in blood phosphorus.
3.Promote the decalcification of osteoclasts and release of Ca3PO4 from the bone matrix, increasing the concentration of blood calcium and phosphorus.
4.Promote the hydroxylation of vitamin D to produce active 1,25 dihydroxy D3, the latter promoting intestinal absorption of calcium from food.
The synthesis and release of parathyroid hormone is controlled by the serum calcium ion concentration, and there is a negative feedback relationship between the two. Low blood calcium stimulates the synthesis and release of parathyroid hormone, which increases blood calcium, while high blood calcium inhibits the synthesis and release of parathyroid hormone, which shifts blood calcium to bone and lowers blood calcium. These effects maintain blood calcium in normal individuals within the normal range.
Second, there are two types of hyperparathyroidism: primary and secondary. Primary hyperparathyroidism is caused by the autonomous secretion of excessive PTH from parathyroid hyperplasia, adenoma or adenocarcinoma, which is not subject to feedback from blood calcium, resulting in a persistent increase in blood calcium. Secondary hyperparathyroidism is usually due to compensatory hypertrophy and hyperfunction of the parathyroid glands due to low blood calcium caused by severe renal insufficiency, vitamin D deficiency, bone lesions, and gastrointestinal malabsorption. Primary hyperparathyroidism can be caused by hyperplasia (12%), proliferative tumor (80%) or adenocarcinoma.
(i) Hyperplasia The main proliferating cells are the principal cells.
Usually all four glands are involved at the same time, but the degree of hyperplasia varies among the four glands. Some glands may be only slightly larger than normal, so the size of the gland cannot be used to determine whether it is normal or not. Sometimes one of the four glands is particularly hyperplastic and is often misdiagnosed as an adenoma
(b) Adenomas can occupy all or part of the gland.
Usually only one gland is involved, and it is extremely rare for both glands to have adenomas at the same time. Both hyperplasia and adenoma are closely packed with cells, so it is sometimes difficult to distinguish them on pathological examination.
(It is difficult to distinguish adenoma from adenocarcinoma in terms of cell formation, but adenocarcinoma should be considered in the following cases.
(1) The gland is adherent to the surrounding tissue.
(2) Metastasis is present.
(iii) Recurrence after resection.
Again, hyperparathyroidism starts slowly and has various clinical manifestations, some patients may be asymptomatic. The more typical clinical manifestations are as follows.
1. Skeletal system.
① early stage: bone pain especially in the low back, hip, rib extremities, local pressure pain may be present.
② late health search: fibrocystic osteitis can appear skeletal deformities and pathological fractures, short stature, walking difficulties, and even bedridden some patients appear bone cysts health search, manifested as local bone bulge.
2, neuromuscular system: tiredness limb weakness, proximal muscles are more, muscle atrophy.
3. Urinary system: polyuria, nocturnal thirst, kidney stones, renal parenchymal sclerosis, renal colic, urinary tract infection.
4. Unexplained hypercalcemia.
5. Central nervous system: memory loss, mood instability, mild personality change, depression, drowsiness, hallucinations, mania, coma.
6. Unexplained pain or arthralgia in many parts of the body.
7. Digestive system: loss of appetite, abdominal distension, indigestion constipation nausea, vomiting, intractable peptic ulcer.