Familial hypocalciuric hypercalcemia: the challenge of diagnosis

Is biochemical screening enough to guide calcium-sensing receptor gene mutational analysis when diagnosing familial hypocalciuric hypercalcemia? A retrospective study

BACKGROUND

The American Association of Endocrine Surgeons suggests screening for familial hypocalciuric hypercalcemia for 24-hour urine calcium <100 mg and for calcium to creatinine clearance ratio <1%. We explored the biochemical and clinical profiles of genetically tested patients to determine the usefulness of these recommendations.

METHODS

This was a retrospective review of patients who underwent analysis of the calcium-sensing receptor gene.

RESULTS

In total, 401 patients were identified between 2005 and 2024; 332 (83%) were negative for a mutation, 44 (11%) were positive, and 25 (6%) had variants of unknown significance. Median serum calcium was lower in patients who were negative (negative 10.1 mg/dL, variants of unknown significance 10.6 mg/dL, positive 10.9 mg/dL). Median urine calcium was lower in patients who were positive (negative 110 mg, variants of unknown significance 149 mg, positive 82 mg). Median parathyroid hormone levels were comparable between groups (negative 65 pg/mL, variants of unknown significance 58 pg/mL, positive 60 pg/mL). Eight of 21 (38%) patients who tested positive had urine calcium >100 mg and 5 of 21 (24%) had urine calcium >200 mg. Eight of 35 (23%) patients who were positive had a calcium to creatinine clearance ratio >1%. Urine calcium and calcium to creatinine clearance ratio receiver operating characteristic curves showed poor performance in identifying patients with familial hypocalciuric hypercalcemia (area under the curve [95% confidence interval]): 0.55 [0.45-0.65] and 0.63 [0.57-0.7], respectively. For positive patients with imaging, sestamibi was inconclusive or nonlocalizing for 13 of 23 and showed multiglandular disease for localizing scans in 7 of 10. Ultrasound was nonlocalizing or equivocal for 11 of 13. In total, 212 of 401 patients (53%) underwent surgery; 100 of 212 were tested preoperatively (0/100 positive, 5/100 variants of unknown significance) and 112 of 212 patients were tested postoperatively (15/112 positive, 10/112 variants of unknown significance).

CONCLUSION

Familial hypocalciuric hypercalcemia demonstrates non-negligible biochemical overlap with primary hyperparathyroidism, with many patients having a urine calcium value greater than the American Association of Endocrine Surgeons suggested threshold for considering genetic evaluation. More frequent genetic testing beyond urine measurements may help identify more patients with familial hypocalciuric hypercalcemia.

Cinacalcet Reverses Short QT Interval in Familial Hypocalciuric Hypercalcemia Type 1

CONTEXT

Familial hypocalciuric hypercalcemia type 1 (FHH-1) defines an autosomal dominant disease, related to mutations in the CASR gene, with mild hypercalcemia in most cases. Cases of FHH-1 with a short QT interval have not been reported to date.

OBJECTIVE

Three family members presented with FHH-1 and short QT interval (<360 ms), a condition that could lead to cardiac arrhythmias, and the effects of cinacalcet, an allosteric modulator of the CaSR, in rectifying the abnormal sensitivity of the mutant CaSR and in correcting the short QT interval were determined.

METHODS

CASR mutational analysis was performed by next-generation sequencing and functional consequences of the identified CaSR variant (p.Ile555Thr), and effects of cinacalcet were assessed in HEK293 cells expressing wild-type and variant CaSRs. A cinacalcet test consisting of administration of 30 mg cinacalcet (8 Am) followed by hourly measurement of serum calcium, phosphate, and parathyroid hormone during 8 hours and an electrocardiogram was performed.

RESULTS

The CaSR variant (p.Ile555Thr) was confirmed in all 3 FHH-1 patients and was shown to be associated with a loss of function that was ameliorated by cinacalcet. Cinacalcet decreased parathyroid hormone by >50% within two hours, and decreases in serum calcium and increases in serum phosphate occurred within 8 hours, with rectification of the QT interval, which remained normal after 3 months of cinacalcet treatment.

CONCLUSION

Our results indicate that FHH-1 patients should be assessed for a short QT interval and a cinacalcet test used to select patients who are likely to benefit from this treatment.

The Nexus of Hyperparathyroidism and Thyroid Carcinoma: Insights into Pathogenesis and Diagnostic Challenges-A Narrative Review

This review investigates the intricate relationship between hyperparathyroidism (HPT) and thyroid carcinoma (TC), aiming to elucidate their coexistence, potential pathogenetic mechanisms, and clinical implications. A systematic search strategy, employing the MeSH terms 'Hyperparathyroidism' and 'Thyroid Carcinoma', spanned publications from 2013 to 2023 across the PubMed, Web of Science, and Scopus databases. Fifteen selected articles were analyzed. Studies unanimously confirm the notable association between primary hyperparathyroidism (PHPT) and thyroid nodules/cancer, with incidences ranging from 2.8% to 47.1%. Key findings reveal a predilection for papillary thyroid carcinoma (PTC) in this association, showcasing varying tumor characteristics and gender disparities. Lower preoperative serum parathyroid hormone (PTH) levels are a potential risk factor for thyroid cancer in PHPT patients. Diverse surgical approaches and tumor characteristics between PHPT and secondary hyperparathyroidism (SHPT) cases were noted. Moreover, this review underscores the scarcity of definitive guidelines in managing concurrent PHPT and thyroid conditions, advocating for comprehensive assessments to enhance diagnostic accuracy and refine therapeutic interventions. Rare coincidental associations, as highlighted by case reports, shed light on unique clinical scenarios. In essence, this review amalgamates evidence to deepen the understanding of the interplay between HPT and TC, emphasizing the need for further research to elucidate underlying mechanisms and guide clinical management.