Management Chronic Hypocalcemia Secondary Hypothyrodism

Goal of Therapy

• The goals of therapy in patients with hypoparathyroidism are to relieve symptoms, to raise and maintain the serum calcium concentration in the low-normal range, eg, 8.0 to 8.5 mg/dL (2.0 to 2.1 mmol/l), and to prevent iatrogenic development of kidney stones.
• Attainment of higher serum calcium values is not necessary and is usually limited by the development of hypercalciuria due to the loss of renal calcium-retaining effects of PTH.

Uptodate

American College of Endocrinology , 2015

Calcium Intravenous calcium is indicated to prevent acute hypocalcemia in patients with chronic hypoparathyroidism who become unable to take or absorb oral supplements. For adults with stable chronic hypoparathyroidism, the dose of oral calcium is typically 1 to 2 g of elemental calcium daily, in divided doses Although calcium carbonate is often used (it is the least expensive), it may be less well-absorbed in older patients and those who have achlorhydria Vitamin D Analogue Several preparations of vitamin D and the various preparations differ in onset of action, duration of action, and cost. Because PTH is required for the renal conversion of calcidiol (25-hydroxyvitamin D [25{OH}D]) to the active metabolite calcitriol (1,25-dihydroxyvitamin D [1,25D]), calcitriol is often regarded as the treatment of choice . The advantages of calcitriol include lack of necessity for endogenous activation, rapid onset of action (hours), and a biologic half-life of about four to six hours. Thiazide Some patients will require the addition of thiazide diuretics (12.5 to 50 mg daily), with or without dietary sodium restriction, to decrease urinary calcium excretion  Second-line therapy  In view of the fact that hypoparathyroidism is a hormonal deficiency, replacement of the missing hormone, ie, PTH 1-84, is a potentially attractive intervention. For patients with chronic hypoparathyroidism who cannot maintain stable serum and urinary calcium levels with calcium and vitamin D supplementation, the addition of recombinant PTH 1-84 is an option

Calcium Calcium is typically provided as calcium carbonate or calcium citrate. Doses ranging up to 9,450 mg per day have been reported, with most patients requiring 1,500 mg elemental calcium daily. Dosing is divided into 2 or 3 split doses to maximize absorption. Vitamin D Analogue Calcitriol improves intestinal calcium absorption and is almost always required. Doses range from 0.125 to 4.0 mcg/day, with most patients requiring 0.25 mcg daily. The doses are typically divided when 1 mcg or more per day is required. Vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol) are occasionally used along with the activated metabolite of vitamin D (calcitriol) and may help to provide smoother control of calcium levels. Thiazide Thiazide diuretics can be added to the regimen when calcium control is difficult or hypercalcuria (>150 mg/24 h) is a problem. Thiazide diuretics enhance distal renal tubular calcium reabsorption, thereby increasing serum calcium and reducing urinary calcium excretion. Hydrochlorothiazide (12.5–50 mg daily) can be effective. A new option for the treatment of hypoparathyroidism recently approved by the U.S. Food and Drug Administration in January 2015, is recombinant human PTH (1-84), which is identical in structure to the fulllength endogenous hormone.

Reference : 

1. Diagnosis and management of hypocalcaemia https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2413335/
2.  AACE/ACE Post Operative Hypoparathyrodism – Definitions & Management http://journals.aace.com/doi/full/10.4158/ep14462.dsc