Increased PTH is seen in all except:

(C) Thyrotoxicosis/None # Chronic renal failure results in phosphate retention and hyperphosphatemia.> Hyperphosphatemia, in turn, induces secondary hyperparathyroidism because phosphate appears to regulate parathyroid hormone secretion directly.> Hypocalcemia develops as the levels of vitamin D 1,25-dihydroxyvitamin D3 (1,25-2 D3) fall because of decreased conversion from the vitamin D metabolite 25-(OH)D3 by damaged kidneys; inhibition of the renal hydroxylase involved in the conversion of 25-(OH)D3 to the more active metabolite 1,25-(OH)D3 by the high levels of phosphorus; and reduced intestinal absorption of calcium because of low levels of 1,25-(OH)2 D3 .> Thyrotoxicosis - since thyroid hormone an increase tissue responsiveness to catacholamine and they can stimulate PTH secretion.> Lithium -| S.calcium + | S. Phosphate f Urine calcium excretion - PTH> Familial hypocalciuric hypercalcaemia - Most cases are associated with loss of function mutation in (ASR genu, which exceedscalcium sending receptor expressed in parathyroid and leads to high level of PTH and the positive hypercalcemia.