Hypocalcemia and hypoparathyroidism (hypoPTH)

Parathyroid hormone (PTH)

• Secreted from chief cells <img src= https://www.drsdiary.com/wp-content/uploads/2021/05/8.-chief-cells.jpg>  when serum calcium (Ca) is low
• 3 actions
  • Increase osteoclastic bone reabsorption
  • Increase intestinal reabsorption
  • Increase calcitriol (D3), tubular reabsorption, phosphate excretion

Etiology

• Chronic kidney disease (MCC), Vitamin D deficiency, thyroid surgery, idiopathic
•  Di George syndrome Di George syndrome – 22q11 deletion, causes cognitive, cardiac, speech/language impairments – mental impairment, cataract, calcified basal ganglia
• Pseudohypoparathyroidism – end organ resistance to hormone (like T2 diabetes)
• Drugs – bisphosphonates, calcitonin <img src= https://www.drsdiary.com/wp-content/uploads/2021/05/8.-calcitonin.jpg>
  (master calcium hormone regulator)
• Hypoalbuminemia Hypoalbuminemia – Calcium is transported via albumin in blood. However, some may be transported as free ions

Pathology

• homeostasis defects, Secondary hyperphosphatemia Secondary hyperphosphatemia – low levels of PTH impairs phosphate excretion

Clinical features

• Neuromuscular irritability, psychosis, paraesthesia, cramps,
• Chvostek and trousseau <img src= https://www.drsdiary.com/wp-content/uploads/2021/05/8.-Chvoskek-and-Trousseau.jpg > signs
• Severe hypoPTH – papilloedema (optic disk swelling), QT syndrome QT syndrome – on ECG usually presents as broad complex QRS (>120ms) this may lead to life threatening ventricular arrhythmias.
• rickets/osteomalacia <img src= https://www.drsdiary.com/wp-content/uploads/2021/05/8-rickets-and-osteomalacia.jpg>

Diagnosis

• clinical, serum calcium, PTH/Vitamin D, hyperphosphatemia
• serum magnesium – hypomagnesemia > hypoparathyroidism

Treatment

• Cholecalciferol
• Alfacalcidol – for chronic kidney disease
• Emergency – Calcium gluconate (I.V)