Causes of Hyperparathyroidism and Hypoparathyroidism

Hyperparathyroidism

Hyperparathyroidism may be primary or secondary.

1.    Primary hyperparathyroidism

a.    Sporadic

      Causes

·         Solitary adenoma (commonest)

·         Cheif cell hyperplasia

·         Carcinoma

 

b.    Familial

·         MEN = multuple endocrine neoplasia type-I Werlmer’s syndrome

·         Autosomal dominant = as with inactivating germ line mutation of MEN-1 TSG on Ch-II

Clinical

• Hyper PTH > 80%
• Benign pituitary adenomas (functioing/non functioning)
• Parcreatoco-duodenal neuroendocine tumors (Beingn / malignant)(gastrinoma, insulinoma, insulinoma, glucagonoma, vipoma & other peptide hormones

MEN-2

·         Occur in MEN-2A & renal in MEN-2B

Familial isolated hyper PTH

·         Increased risk of PT carcinoma

2.    Secondary hyper PTH

Due to chronic renal failure,

D  Decreased calcitriol leads to decreased calcium & PO4 retention causing proliferation of PT cells and increase in gland parendepmal mass

3.    Tertiary hyper PTH

Renal osteodystrophy, following renal transplantation, development of autonomous hyper function of PT tissue & increased calcemia 

4.    Parathyroid Ca

5.    Persistant / recurrent hyper PTH

Ca occuring more than 1 yr after creative parathyroidectomy

Causes

·      Missed pathology at 1^st surgical procedure

·      Graft dependent recuence

·     Parathyromatosis disseminated nodules of PT tissue within soft tissue of neck & suspicious mediastenemia caused by abnormal PT tissue at initial surgery. (reoperative PT surgery,risk of recurrent laugeal nerve injury & postopCa)

Causes of hypoparathyroidism

1.    Primary hypoparathyroidism

PTH deficiency

Causes

1. Surgical damage to glands (common)

• During thyroidectomy
• Radical neck dissection
• Resection of PT gland in PT hyperplasia

2.    Radiation therapy to neck

3.    Damage from

• Infection
• Metastatic tumor
• Infiltration by granuloma (TB, sarcoidosis)
• Heavy metals (Wilsons, hemocheomatosis, transfusion hemosiderosis)

4.    Hormone – Resistant (inherited) (Pseudohypoparathyroidism = PHP)

End organ resistance to PTH, plasma levels of which are hight in response to hypocalcemia

PHP = type (1a & 1b)

·         Inability of PTH to generate an increase in urinary (AMP, PHP = type-II)

PHP type-II

·         Inability of PTH to generate an increase in phosphaturic response

Idopathic

Dysembryogenesis (Di-George’s syndrome)

Appears as familial disorder, may have autoimmune basis presents at puberty where it is associated with mucoutaneous candidiasis due to immune def & other endocrine disorders.

Magnesium Deficiency

·            Serum magnesium < 0.4 mmol/L)

·            Suppresion of PTH secretion becoming unresponsive to calcium therapy unless patient becomes magnesium-replete.