VITAMIN D AND HYPERPARATHYROIDISM

VITAMIN D , HYPERPARATHYROIDISM , METABOLISM OF VITAMIN D

1. VITAMIN D & HYPERPARATHYROIDISM - Dr.Apoorva.E PG,DCMS

2. VITAMIN-D AND ITS METABOLISM Vitamin D is a fat soluble vitamin. It is the precursor of 1,25-dihydroxycholecalciferol which is the active form of vitamin D secreted by the kidney, under the control of parathyroid hormone. Its deficiency causes rickets in children and osteomalacia in adults.

3. SUNLIGHT AS A SOURCE Sunlight in the ultraviolet band

4. DIETARY SOURCES Vitamin D3

5. CALCIUM HOMEOSTASIS SHOWING INTERACTION BETWEEN PTH,VITAMIN D AND CALCIUM

6. HYPERPARATHYROIDISM Parathyroid glands are four glands located behind the thyroid gland in the front of the neck. They produce a hormone called parathyroid hormone ( parathormone ). PTH regulates serum calcium levels in the body. Hyperparathyroidism is the overproduction of this hormone.

7. ACTION OF PTH

8. CLASSIFICATION OF HYPERPARATHYROIDISM Primary Secondary Tertiary

9. PRIMARY HYPERPARATHYROIDISM Excess secretion of PTH from one or more parathyroid glands. Prevalence is 1 in 800,2-3times more common in women,average age being 55years. Is associated with familial MEN syndromes - MEN I: Primary hyperparathyroidism+pituitary tumors+pancreatic tumors - MEN IIa : Primary hyperparathyroidism+medullary carcinoma of thyroid+pheochromocytoma

10. ETIOLOGY -Single adenoma in 90% -Nodular hyperplasia in 5% -Multiple adenomas in 4% -Carcinoma in 1% .

11. The signs and symptoms of primary hyperparathyroidism are those of hypercalcemia . CLINICAL FEATURES

12.  Patients present with kidney stones,nephrocalcinosis,diabetes insipidus ( polyuria and polydipsia ).These ultimately lead to renal failure.  bone-related complications like osteitis fibrosa (bone pain and pathological fractures), osteoporosis,osteomalacia and  arthritis.  gastrointestinal symptoms of  constipation,anorexia,nausea , vomiting,peptic ulcers,acute pancreatitis.

13. cardiovascular system involvement leading to hypertension,bradycardia,shortened QT interval and left ventricular hypertrophy . -  central nervous system symptoms include lethargy,fatigue,depression,memory loss, psychosis,ataxia,delirium and coma. - other signs include proximal muscle weakness,itching,band keratopathy of the eyes.

14. DIAGNOSIS Serum calcium levels are elevated. Parathyroid hormone level is abnormally high. There is hypophosphatemia and increase in 24-hour urinary calcium excretion. DEXA scan shows skeletal involvement.

15. Pathognomonic X-ray changes include salt and pepper degranulation in the skull and subperiosteal bone resorption in the phalanges.

16. Imaging of renal tract (X-ray, ultrasound) can demonstrate renal calculi. Localisation of parathyroid tumors by technetium scan,ultrasound,CT of the neck followed by FNAC.

17. TREATMENT Management of acute hypercalcemia by rehydration with normal saline,bisphosphonates,haemodialysis . Medical line : -Monitor serum creatinine levels and calcium levels every 6 months.DEXA scan on an annual basis. -Avoid thiazide diuretics. -Maintain high oral fluid intake. -Improving bone mineral density and achieving calcium homeostasis by calcimimetics and HRT.

18. 3. Surgery : -Is indicated in patients with complications and in younger age group. -Minimally invasive surgery to excise solitary adenoma, Subtotal parathyroidectomy in case of diffuse hyperplasia are being done.

19. SECONDARY HYPERPARATHYROIDISM It occurs when PTH secretion is increased to compensate for prolonged hypocalcemia .   It is seen in patients with chronic renal failure where the failing   kidneys  do not convert vitamin D  to its active form and they do not excrete phosphate. Excess phosphate combines with calcium to form calcium phosphate. Both processes lead to hypocalcemia,cause hyperplasia of all parathyroid tissue and hence secondary hyperparathyroidism.

20. Secondary hyperparathyroidism can also result from malabsorption of vitamin D due to chronic pancreatitis,small bowel disease,bariatric surgery. CLINICAL FEATURES : are mostly of renal failure.If it is due to vitamin D deficiency,limb deformities,pathological fractures occur.

21. INVESTIGATIONS : Serum calcium levels are low.PTH levels are raised. Phosphate levels depend on etiology (e.g. high in renal disease, low in vitamin D deficiency). Radiology shows evidence of bone disease. TREATMENT : Medical line is the mainstay. The underlying condition needs to be treated -correcting vitamin D deficiency. -treatment of chronic kidney disease (Calcium supplementation. Treatment with vitamin D and its analogues. Calcimimetics )

22. TERTIARY HYPERPARATHYROIDISM In a small proportion of cases of secondary hyperparathyroidism,continuous stimulation of the parathyroids results in adenoma formation and unregulated PTH secretion. Even correction of the underlying cause will not stop excess PTH secretion i.e parathyroid gland hypertrophy becomes irreversible.

23. CLINICAL FEATURES : Symptoms and signs are due to hypercalcemia so presentation is similar to primary hyperparathyroidism . INVESTIGATIONS : Serum calcium and PTH levels are raised. Phosphate levels are often high. TREATMENT : Total or subtotal parathyroidectomy is the recommended treatment. Autotransplantation of parathyroid tissue in the forearm is also commonly carried out .

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