Hypercalcemia in a patient with primary hyperparathyroidism and acromegaly: distinct roles of growth hormone and parathyroid hormone in the development of hypercalcemia

Characterization of vitamin D metabolism in active acromegaly in the setting of bolus (150,000 IU) cholecalciferol treatment

PURPOSE

To reveal distinctive features of vitamin D metabolism in patients with active acromegaly compared to healthy individuals, particularly in the setting of cholecalciferol treatment.

METHODS

The study group included 34 adults with active acromegaly, and the control group included 30 apparently healthy adults with similar age, sex, and BMI. All participants received a single dose (150,000 IU) of cholecalciferol aqueous solution orally. Laboratory assessments including serum vitamin D metabolites (25(OH)D₃, 25(OH)D₂, 1,25(OH)₂D₃, 3-epi-25(OH)D₃ and 24,25(OH)₂D₃), free 25(OH)D, vitamin D-binding protein (DBP) and parathyroid hormone (PTH) as well as serum and urine biochemical parameters were performed before the intake and on Days 1, 3, and 7 after the administration. All data were analyzed with nonparametric statistics.

RESULTS

Patients with acromegaly had tendency to lower baseline 25(OH)D₃ levels (p = 0.05) and lower 25(OH)D₃ levels (p < 0.05) during the follow-up. They were also characterized by PTH suppression (lower baseline PTH levels and lower prevalence of secondary hyperparathyroidism), altered production of main vitamin D metabolites (higher 1,25(OH)₂D₃ and lower 24,25(OH)₂D₃ levels with corresponding lower 25(ОН)D₃/1,25(ОН)₂D₃ and higher 25(ОН)D₃/24,25(ОН)₂D₃ ratios) as well as concordant biochemical features (higher levels of serum phosphorus and albumin-adjusted calcium levels) throughout the study (p < 0.05). The acromegaly group showed an increase in DBP levels after cholecalciferol intake as opposed to the control group (p < 0.05) and had lower increase in free 25(OH)D levels (p < 0.05). Δ25(OH)D₃ was similar between the groups (p > 0.05), showed a negative correlation with the disease activity markers-both IGF-1 levels (r = -0.44, p < 0.05) and fasting GH levels (r = -0.56, p < 0.05)-and lacked correlation with BMI in the acromegaly group (p > 0.05).

CONCLUSION

Patients with active acromegaly have dysregulated vitamin D metabolism characterized by higher 1,25(ОН)₂D₃, lower 24,25(ОН)₂D₃ and altered DBP production. The response to vitamin D supplementation in acromegaly patients might be influenced by hormonal excess. Obtained results require reproducibility check and further study to develop specific clinical recommendations.

TRIAL REGISTRATION

NCT04844164 (release date: April 9, 2021; retrospectively registered).

Acromegaly and non-parathyroid hormone-dependent hypercalcemia: a case report and literature review

BACKGROUND

Hypercalcemia associated with acromegaly is mostly parathyroid hormone (PTH)-dependent, being caused by parathyroid hyperplasia or adenoma, which are common in individuals with multiple endocrine adenomatosis-1 (MEN-1). The rare occurrence of non-PTH-dependent hypercalcemia associated with acromegaly is attributable to complex factors involving increased intestinal calcium absorption, enhanced bone calcium release, and reduced urinary calcium elimination. Although patients with acromegaly often have mild hyperphosphatemia and hypercalciuria, clinically significant hypercalcemia is extremely rare.

CASE PRESENTATION

Here we present a case of non-PTH-dependent hypercalcemia associated with a growth hormone- (GH) and prolactin- (PRL) co-secreting pituitary macroadenoma. A 37-year-old Chinese man presented with a 6-year history of increasing ring and shoe sizes and was referred to the West China Hospital of Sichuan University for treatment of acromegaly. Pituitary magnetic resonance imaging (MRI) showed a 2.0 × 1.7 × 1.9 cm macroadenoma. Laboratory examinations revealed high serum concentrations of GH and PRL with mild hypercalcemia, hyperphosphatemia, hypercalciuria, inhibited PTH concentration, and increased bone turnover markers. Administration of cabergoline together with somatostatin resulted in sharp decreases in his GH, PRL, and serum and urinary calcium concentrations. These values were further reduced 5 months later and his PTH and bone turnover markers gradually returned to within the normal range.

CONCLUSIONS

Mild hyperphosphatemia and hypercalciuria are common in individuals with acromegaly and deserve attention because they may contribute to osteoporosis and urolithiasis. However, overt hypercalcemia is rare in such individuals. It is usually attributable to a coexisting parathyroid hyperplasia or adenoma, rarely being non-PTH-dependent. In such cases, the hypercalcemia is attributable to excessive PRL and hypogonadism and reverses with remission of acromegaly.

[Vitamin D metabolism in hypercorticism and acromegaly]

Due to the high prevalence of low vitamin D levels in the overwhelming majority of regions of the world and discovery of extra-skeletal effects of vitamin D, the issue of maintaining adequate levels of vitamin D in the blood remains extremely relevant, especially in people with high risk of severe deficiency. To date, few studies have been performed on the features of vitamin D metabolism in disorders such as hypercorticism and acromegaly. However, vitamin D deficiency in such patients, according to available literature, may be more widespread and more pronounced than in general population. It is now recommended to use standard prophylactic and therapeutic doses of vitamin D for the treatment of these diseases, which may not satisfy the therapeutic goals specific to each disease. This review provides information on normal vitamin D metabolism, as well as literature data on the possible relationship and mutual influence between these endocrinopathies and vitamin D metabolism.

Systemic Complications of Acromegaly and the Impact of the Current Treatment Landscape: An Update

Acromegaly is a chronic systemic disease with many complications and is associated with increased mortality when not adequately treated. Substantial advances in acromegaly treatment, as well as in the treatment of many of its complications, mainly diabetes mellitus, heart failure, and arterial hypertension, were achieved in the last decades. These developments allowed change in both prevalence and severity of some acromegaly complications and furthermore resulted in a reduction of mortality. Currently, mortality seems to be similar to the general population in adequately treated patients with acromegaly. In this review, we update the knowledge in complications of acromegaly and detail the effects of different acromegaly treatment options on these complications. Incidence of mortality, its correlation with GH (cumulative exposure vs last value), and IGF-I levels and the shift in the main cause of mortality in patients with acromegaly are also addressed.

Calcium and Bone Turnover Markers in Acromegaly: A Prospective, Controlled Study

CONTEXT

Acromegaly has been associated with calcium-phosphate and bone turnover alterations. Controlled studies of these interactions are sparse.

OBJECTIVE

To evaluate calcium and bone metabolism in active and treated acromegaly.

DESIGN/SETTING/PATIENTS

We conducted a controlled, prospective study at a tertiary referral center. We studied 22 patients with acromegaly referred for surgical or medical therapy (ACM) and 22 with nonfunctioning pituitary adenomas referred for surgery (control).

MAIN OUTCOME MEASURES

Calcium (serum and urine), phosphorus, parathyroid hormone (PTH), 25-hydroxy- and 1,25-dihydroxy-vitamin D, bone turnover markers [serum C-terminal telopeptide of type 1 collagen (CTX) and procollagen type 1 N-terminal propeptide (P1NP)], and cytokines [receptor activator of nuclear factor κB ligand (RANK-L) and osteoprotegerin (OPG)] at baseline and 3 to 6 months after treatment.

RESULTS

At baseline, the ACM group had lower PTH levels than controls (36.3 ± 13.9 pg/mL vs 56.0 ± 19.9 pg/mL) and higher phosphorus (4.34 ± 0.71 mg/dL vs 3.55 ± 0.50 mg/dL) (P < 0.01). Groups had similar levels of serum and urine calcium and 25-hydroxy- and 1,25-dihydroxy-vitamin D. The ACM group had higher bone turnover markers than control; P1NP and CTX were strongly correlated (r2 = 0.82, P < 0.05). CTX was dependent on age and disease group but not on sex or gonadal status. After treatment of acromegaly, serum calcium (9.52 ± 0.43 mg/dL to 9.26 ± 0.28 mg/dL), phosphorus (4.34 ± 0.71 mg/dL to 3.90 ± 0.80 mg/dL), and CTX (0.91 ± 0.75 ng/mL to 0.63 ± 0.68 ng/mL) decreased, while PTH increased (36.3 ± 13.9 pg/mL to 48.9 ± 16.7 pg/mL) (P < 0.01). 25-hydroxy-vitamin D, P1NP, and RANK-L/OPG ratio did not change significantly.

CONCLUSION

Acromegaly patients exhibited PTH-independent calcium-phosphate alterations and enhanced coupled bone formation and resorption. Within 6 months of treatment, bone resorption decreased, whereas RANK-L/OPG changes were inconsistent.

Vitamin D across growth hormone (GH) disorders: From GH deficiency to GH excess

The interplay between vitamin D and the growth hormone (GH)/insulin-like growth factor (IGF)-I system is very complex and to date it is not fully understood. GH directly regulates renal 1 alpha-hydroxylase activity, although the action of GH in modulating vitamin D metabolism may also be IGF-I mediated. On the other hand, vitamin D increases circulating IGF-I and the vitamin D deficiency should be normalized before measurement of IGF-I concentrations to obtain reliable and unbiased IGF-I values. Indeed, linear growth after treatment of nutritional vitamin D deficiency seems to be mediated through activation of the GH/IGF-I axis and it suggests an important role of vitamin D as a link between the proliferating cartilage cells of the growth plate and GH/IGF-I secretion. Vitamin D levels are commonly lower in patients with GH deficiency (GHD) than in controls, with a variable prevalence of insufficiency or deficiency, and this condition may worsen the already known cardiovascular and metabolic risk of GHD, although this finding is not common to all studies. In addition, data on the impact of GH treatment on vitamin D levels in GHD patients are quite conflicting. Conversely, in active acromegaly, a condition characterized by a chronic GH excess, both increased and decreased vitamin D levels have been highlighted, and the interplay between vitamin D and the GH/IGF-I axis becomes even more complicated when we consider the acromegaly treatment, both medical and surgical. The current review summarizes the available data on vitamin D in the main disorders of the GH/IGF-I axis, providing an overview of the current state of the art.

Diagnosis of acromegaly: state of the art

INTRODUCTION

Biochemical diagnosis of acromegaly relies on measurement of insulin-like growth factor-1 (IGF-1) and growth hormone (GH). An elevated IGF-1 level above the age- and gender-specific normal range and nonsuppression of GH to oral glucose load to a nadir < 0.4 ng/ml in sensitive assays are currently considered diagnostic of acromegaly. Lack of normative data for both IGF-1 and GH across a wide range of populations and ethnicities, interassay and intraassay laboratory variability, pulsatility of GH secretion, and effects of medications and hormones may confound interpretation of these biochemical tests.

AREAS COVERED

Clinical situations in which acromegaly should be suspected and/or investigated. Strengths and limitations of current IGF-1/GH assays are discussed. Clinical scenarios with discordant GH suppression test and IGF-1 levels and, briefly, acromegaly in pregnancy, prolactin-cosecreting tumors, familial acromegaly, and nonpituitary acromegaly are also discussed.

EXPERT OPINION

Serum IGF-1 is the cornerstone and in most cases the stand-alone test in the diagnosis and follow-up in patients with acromegaly. Diagnosis depends on the accurate and reliable measurement of serum IGF-1. GH suppression testing is currently used in limited clinical setting. Standardization of IGF-1 assay and development of normative data across a wide population base are needed. Newer bioassays for IGF-1 hold promise for future.