CAUSES :
1. PARATHYROID HORMONE ABSENT
- HEREDITARY HYPOPARATHYROIDISM
* IDIOPATHIC
* DIGEORGE SYNDROME
* VELOCARDIOFACIAL SYNDROME
* AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE-1
* AUTOSOMAL DOMINANT HYPOCALCEMIA
* KEARNS-SAYRE SYNDROME
* MELAS SYNDROME
- ACQUIRED HYPOPARATHYROIDISM
* POSTOPERATIVE
* RADIATION INDUCED
* DAMAGE IN PT WITH HEMOCHROMATOSIS & HEMOSIDEROSIS AFTER REPEATED BLOOD TRANSFUSION
* TRANSIENT HYPOTHYROIDISM AFTER SURGERY FOR PARATHYROID GLAND
2. PARATHYROID HORMONE INEFFECTIVE
- CHR RENAL FAILURE
- ACTIVE VIT D LACKING
- DECREASED DIETARY INTAKE OR SUNLIGHT
- DEFECTIVE METABOLISM LIKE IN
* ANTICONVULSANT THERAPY
* VIT D DEPENDANT RICKETS TYPE I
3. PARATHYROID HORMONE OVERWHELMED
- SEVERE ACUTE HYPERPHOSPHATEMIA
- TUMOR LYSIS
- AC RENAL FAILURE
- RHABDOMYOLYSIS
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ANOTHER CLASSIFICATION FOR D.D. :
1. IATROGENIC
- PARATHYROID SURGERY
- SURGERY FOR THYROID, LARYNGEAL & NECK MALIGNANCIES
- IRRADIATION
- HUNGRY BONE SYNDROME AFTER PARATHYROIDECTOMY FOR HYPERPARATHYROIDISM
2. AUTOIMMUNE CAUSES
- AUTOIMMUNE POLYENDOCRINE SYNDROME TYPE-1
- AUTOIMMUNE HYPOPARATHYROIDISM ISOLATED, SPORADIC OR IN FAMILIAL FORM
3. CONGENITAL CAUSES
- ISOLATED PRIMARY HYOPARATHYROIDISM
- X-LINKED PRIMARY HYPOPARATHYROIDISM
- X AUTOSOMAL-RECESSIVE PRIMARY HYPOTHYROIDISM
- DIGEORGE SYNDROME ( BRANCIAL DYSGENESIS)
- CHROMOSOMAL DEFECTS DUP(1Q), DEL(5P), DUP(8Q), DEL(10Q), DEL(22Q)
- MONOGENIC HYPOPARATHYROIDISM
- ISOLATED AUTOSOMAL-DOMINANT CONDITIONS
- ISOLATED AUTOSOMAL-RECESSIVE CONDITIONS
- VELOCARDIOFACIAL ( SHPRINTZEN) SYNDROME
- ZELLWEGER SYNDROME
- TERATOGENIC EFFECTS
- DIABETIC EMBRYOPATHY
- FETAL ALCOHOL SYNDROME
- RETINOID EMBRYOPATHY
- ASSOCIATIONAL ARHINENCEPHALIA &/OR DIGEORGE SYNDROME & THE COLOBOMA, HEART DISEASE, CHOANAL ATRESIA, RETARDED GROWTH & DEVELOPMENT, GENITAL ANOMALIES, EAR ANOMALIES (CHARGE) SYNDROME &/OR DIGEORGE SYNDROME
-CARDIOFACIAL-DIGEORGE-KENNY-CAFFEY SYNDROME ( IE, ABSENT PARATHYROID TISSUE, GROWTH RETARDATION, MEDULLARY STENOSIS OF TUBULAR BONES )
- KEARNS-SAYRE SYNDROME ( IE, MITOCHONDRIAL MYOPATHY, OPHTHALMOPLEGIA, RETINAL DEGENERATION, CARDIAC CONDUCTION DEFECTS, PRIMARY HYPOPARATHYROIDISM )
- BARAKAT SYNDROME ( IE, PRIMARY HYPOPARATHYROIDISM, NERVE DEAFNESS, STEROID RESISTANT NEPHROSIS )
- HYPOPARATHYROIDISM WITH SHORT STATURE, MENTAL RETARDATION & SEIZURES
- IN ADDITION TO ABOVE LIST SEVERAL OTHER GENETIC DEFECTS CAUSE PRIMARY HYPOPARATHYROIDISM
4. CAUSES RELATED TO METAL OVERLOAD ( ION DEFICIENCY )
- HEMOCHROMATOSIS & THALASSEMIA
- WILSON DISEASE
- HYPERMAGNESEMIA
- ALUMINIUM DEPOSITION WITHIN THE PARATHYROID GLAND IN END STAGE RENAL DISEASE PTS ON HEMODIALYSIS
- HYPOMAGNESEMIA
5. INFILTRATIVE CAUSES
- METASTATIC DISEASES
- GRANULOMATOUS DISEASES
- AMYLOIDOSIS
- SYPHILIS
- PROGRESSIVE SYSTEMIC SCLEROSIS
CLINICAL SIGNIFICANT HYPOCALCEMIA IS NOT ALWAYS APPARENT IN THESE PTS
6. NEONATAL CAUSES
- UNORN BABY OF A MOTHER WITH HYPERCALCEMIA
OTHER TESTS :
* HYPOMAGNESEMIA - IS ASSOCIATED WITH BOTH DEFICIENT PTH RELEASE & IMPAIRED RESPONSIVENESS TO PTH CAUSING HYPOCALCEMIA. CORRECTING HYPOMAGNESEMIA CORRECTS HYPOCALCEMIA & PLASMA PTH ALSO.
* MEASURE 25-HYDROXY VIT D - TO EXCLUDE VIT D DEFICIENCY AS A CAUSE FOR HYPOCALCEMIA
* SERUM PHOSPHORUS - PTH IS A PHOSPHATURIC HORMONE, IN ITS ABSENCE PHOSPHATE LEVELS IN BLOOD RISE.
* SERUM PTH - LOW
* SERUM CALCIUM - LOW
MEASUREMENT OF IONISED CALCIUM IS IDEAL AS TOTAL SERUM CALCIUM IS EFFECTED BY TOTAL SERUM PROTEIN OR ALBUMIN LEVELS. SIMPLE RULE - SERUM TOTAL CALCIUM CONC FALLS BY 0.8 MG% FOR EVERY 1-GM FALL IN SERUM ALBUMIN. THIS RULE ASSUMES THAT NORMAL ALBUMIN EQUALS 4.0 GM% & NORMAL CALCIUM 10.0 MG%
* PRIMARY HYPOPARATHYROIDISM - LOW PTH & LOW CALCIUM
* PSEUDOHYPOPARATHYROIDISM - RAISED PTH DUE TO RESISTANCE AT RECEPTOR SITES
* SECONDARY HYPOPARATHYROIDISM - PTH LOW & CALCIUM HIGH