Changes in Calcium Homeostasis in Acromegaly Treated by Pituitary Adenomectomy*

Abstract

Patients with acromegaly have alterations in mineral metabolism. To determine the effect of correction of excess GH secretion on calcium metabolism, we studied 12 acromegalic patients before and 3-4 weeks after pituitary adenomectomy. Treatment of acromegaly resulted in significant decreases in both serum calcium [from 9.3 +/- 0.2 to 8.7 +/- 0.1 mg/dl (mean +/- SEM); P less than 0.01] and urinary calcium excretion (from 200 +/- 24 to 88 +/- 12 mg/24 h; P less than 0.0002). Serum phosphate also decreased significantly (P less than 0.01) from 4.8 +/- 0.2 to 4.3 +/- 0.2 mg/dl. Both serum immunoreactive PTH and calcitonin levels were normal initially and did not change after surgery. The mean serum 25-hydroxyvitamin D (25OHD) level was significantly (P less than 0.01) lower and the 1,25-dihydroxyvitamin D [1,25-(OH)2D] level was significantly (P less than 0.0001) higher in acromegaly compared with measurements in 25 normal subjects. After surgery, the serum 25OHD level did not change; however, the serum 1,25-(OH)2D concentration fell significantly (P less than 0.0001) from 60 +/- 4 to 43 +/- 2 pg/ml. A positive correlation was found between the decrements in urinary calcium excretion and the serum 1,25-(OH)2D level when the comparison was made between the decrements as percentages of pretreatment values (r = 0.64; P less than 0.05). The accumulated data suggest that the hypercalciuria in acromegaly might be due to intestinal calcium hyperabsorption, which could be attributed to the elevated circulating 1,25-(OH)2D level. Excessive GH secretion might stimulate the production of 1,25-(OH)2D and might also directly stimulate calcium absorption.

Long-term Treatment of Acromegaly with Lanreotide: Evidence of Increased Serum Parathormone Concentration

“…Serum total calcium level is generally within the upper normal range and hypercalciuria is frequent in acromegalics [12][13][14]: this is due to the increased intestinal calcium absorption secondary to enhanced renal synthesis of 1,25 (OH) 2 vit D [4,8,15,16], although the increased bone resorption may contribute [3]. Furthermore, acromegalic patients show increased renal phosphate reabsorption [17] resulting in serum phosphate levels within or above normal range [18].…”

“…A significant decrease in circulating levels of calcium, phosphate and 1,25 (OH) 2 vit D have been observed in patients with acromegaly after pituitary adenectomy [4]. This can be explained by the decrease in GH levels with diminished effects on renal 1a-hydroxylase activity and on renal phosphate reabsorption [4,5].…”

“…It is known that acromegalic patients show abnormalities in calcium-phosphate metabolism and morphologic skeleton alterations [3]. Pituitary adenectomy corrects many of these biochemical alterations [4,5].…”

“…Few authors have reported that long treatment with octreotide significantly corrects some biochemical abnormalities of bone turnover, but they also reported that it induces an increase of iPTH [8,9] in contrast to pituitary adenectomy [4] and bromocriptine therapy [10].…”

Excessively high soluble Klotho in patients with acromegaly

“…It leads to high levels of serum phosphate in the presence of an ª 2012 The Association for the Publication of the Journal of Internal Medicineincreased GFR [12][13][14] and induces insulin resistance (IR) and hyperglycaemia despite reduced visceral fat. The mechanisms underlying both high phosphate and high glucose levels (which have been epidemiologically linked to increased morbidity and mortality in the general population [15,16]) in acromegaly require further clarification.…”