Differentiating AVP deficiency and primary polydipsia: a clinical and biochemical perspective

Erdogan Beril Turan; Muzaffer Deniz; balsak belma tural; Caglar Keskin; Polat Şefika Burcak; Oya Topaloglu; Reyhan Ersoy; Bekir Cakir

doi:10.1530/endoabs.110.P917

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Endocrine Abstracts (2025) 110 P917 | DOI: 10.1530/endoabs.110.P917

ECEESPE2025 Poster Presentations Pituitary, Neuroendocrinology and Puberty (162 abstracts)

Differentiating AVP deficiency and primary polydipsia: a clinical and biochemical perspective

Beril Turan Erdogan ¹ , Muzaffer Deniz ¹ , belma tural balsak ¹ , Caglar Keskin ¹ , Şefika Burçak Polat ² , Oya Topaloglu ² , Reyhan Ersoy ² & Bekir Cakir ²

Author affiliations

¹Ankara Bilkent City Hospital, Department of Endocrinology and Metabolism, Ankara, Türkiye; ²Ankara Yildirim Beyazit University Faculty of Medicine, Department of Endocrinology and Metabolism, Ankara, Türkiye

JOINT3487

Background: Polyuria and polydipsia require differentiation between arginine vasopressin (AVP) deficiency and primary polydipsia (PP), as both involve excessive water intake and urine output but have distinct pathophysiology. This study aimed to compare biochemical, clinical, and hormonal differences between AVP deficiency and PP to identify distinguishing diagnostic markers.

Methods: A retrospective observational study was conducted on 36 patients who underwent a water deprivation test at Ankara Bilkent City Hospital between February 2019 and December 2024. Patients were categorized as AVP deficiency (complete or partial) and PP based on clinical and biochemical findings. Plasma and urine osmolarity, sodium, chloride, magnesium, and anterior pituitary hormones (LH, GH, ACTH\.) were analyzed.

Results: Among 36 patients, 55.6% had AVP deficiency, while 22.2% were diagnosed with PP. Nocturia was significantly more prevalent in AVP deficiency (96.2%) than PP (12.5%, P < 0.001). Fluid intake exceeded 10 liters/day in 62.5% of PP patients, whereas AVP deficiency patients typically consumed 5–10 liters/day. Plasma osmolarity was lower in PP, and urine osmolarity was significantly lower in PP than AVP deficiency (P = 0.011). Sodium (P = 0.030), chloride (P = 0.040), and magnesium (P = 0.010) were significantly reduced in PP. Hormonal analysis showed elevated LH (P = 0.011) and GH (P = 0.028) in PP compared to AVP deficiency.

Discussion: Findings suggest that nocturia frequency, fluid intake patterns, and specific biochemical markers (sodium, chloride, magnesium) may assist in differentiating PP from AVP deficiency. The lower urine osmolarity in PP highlights impaired urine concentration despite intact AVP function, while electrolyte disturbances suggest altered water balance regulation. Additionally, although LH and GH levels were statistically higher in PP, this does not necessarily imply clinical significance. These distinctions reinforce the importance of integrating biochemical, clinical, and hormonal assessments for accurate diagnosis.

Table: Key Biochemical and Hormonal Differences Between AVP Deficiency and PP.
Parameter	AVP Deficiency (n = 26)	PP (n = 8)	P-value
Nocturia (%)	96.2	12.5	<0.001
Urine Osmolarity (mOsm/l)	101±48	129±41	0.011
Sodium (mEq/l)	142±3	138±4	0.030
Chloride (mEq/l)	108±3	105±4	0.040
Magnesium (mg/dl)	2.0±0.2	1.8±0.1	0.010
LH (U/l)	5.65±7.77	11.78±11.99	0.011
GH (ng/mL)	0.27±0.54	0.43±0.39	0.028

Conclusion: This study underscores the diagnostic value of urine osmolarity, plasma sodium, chloride, magnesium, and anterior pituitary hormones in differentiating AVP deficiency from PP. Incorporating these markers into routine evaluation may improve diagnostic precision and guide targeted management strategies. Further large-scale studies are recommended to validate these findings and optimize diagnostic criteria.