Sheehan syndrome presenting as early post-partum hyponatraemia

Eric Boulanger, Dominique Pagniez, Stéphane Roueff, Raynald Binaut, Anne-Sylvie Valat1, Nathalie Provost1, Remy Leroy2, Xavier Codaccioni1 and Philippe Dequiedt

Service de Néphrologie B, Hôpital Calmette, 1 Service de Suites de Couches, Maternité Jeanne de Flandre and 2 Service d'Endocrinologie, Clinique Marc Linquette, CHRU Lille, Lille, France

Correspondence and offprint requests to: Dr Eric Boulanger, Service de Néphrologie B, Hôpital Calmette, Boulevard du Pr. J. Leclerc, 59037 Lille Cedex, France.

Keywords: antidiuretic hormone; hyponatraemia; hypopituitarism; pregnancy; Sheehan syndrome



   Introduction
 Top
 Introduction
 Case
 Discussion
 References
 
Post-partum anterior pituitary necrosis (Sheehan syndrome) occurs rarely, and seldom causes hypopituitarism. Hyponatraemia is an initial manifestation of post-partum pituitary insufficiency. Post-partum hyponatraemia is usually caused by surgical procedure or inappropriate rehydration. We report on a third case of early and acute hyponatraemia with inappropriate secretion of antidiuretic hormone occurring 10 days after vaginal delivery with severe blood loss.



   Case
 Top
 Introduction
 Case
 Discussion
 References
 
A 30-year-old woman presented in active labour at the 38th week of gestation. Two years previously, a Caesarean section was performed due to pelvic–fetal disproportion. The patient had spontaneous vaginal delivery, followed by severe blood loss because of uterine scar disjunction. Hysterectomy was performed to control blood loss: transient disseminated intravascular coagulation occurred.

The patient had normal biochemical data for 6 days in the intensive care unit. Ten days after hysterectomy, she complained of asthenia and failure to lactate. Hydration was clinically normal. Blood pressure was 120/75 mmHg. Red and white blood cell and platelet counts were within normal values. The biochemical data indicating acute hyponatraemia are presented in Table 1Go. Low blood osmolality and elevated urine osmolality suggested inappropriate secretion of antidiuretic hormone.


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Table 1. Biochemical results 10 days after delivery
 
Panhypopituitarism was suspected, and confirmed by hormonal level determination and test results as seen in Table 2Go. Severe adrenocortical insufficiency with a low cortisol level was found. Severe diminution of luteinizing and follicle-stimulating hormone levels and mild hypothyroidism were also found.


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Table 2. Hormonal level and test results
 
After 3 days of water deprivation, the sodium concentration was normal. No pituitary abnormality was found with magnetic resonance imaging.

With hormonal substitution, 30 mg/day hydrocortisone and 100 µg/day L-thyroxine, no relapse of inappropriate secretion of antidiuretic hormone has occurred 18 months after delivery. Subsequent magnetic resonance imaging showed pituitary atrophy.



   Discussion
 Top
 Introduction
 Case
 Discussion
 References
 
Post-partum anterior pituitary necrosis is an uncommon complication of haemorrhagic shock after delivery. This syndrome causes a variety of signs and symptoms, usually occurring long after delivery. The diagnosis is often fortuitous when patients are explored for suspected hypothyroidism, amenorrhoea, glucocorticoid dysfunction or metabolic abnormalities. Many years after haemorrhagic shock, chronic hyponatraemia can reveal Sheehan syndrome [13].

Hyponatraemia as the presenting manifestation of Sheehan syndrome in the early post-partum period has been reported twice [4,5]. Several hypotheses have been proposed to explain hyponatraemia in the presence of hypopituitarism, i.e. dysfunction of the anterior hypophysis.

Inappropriate secretion of antidiuretic hormone is known to occur in states of adrenocorticotropin deficiency [6,7]. Glucosteroids have been shown to reverse the impaired water diuresis of this disorder by increasing the renal excretion of solute-free water. One study [8] reported that the plasma arginine vasopressin level was abnormally elevated during mild dehydration, and remained above the normal range despite haemodilution in patients with untreated adrenocorticotropin deficiency demonstrating a delayed water diuresis. Glucosteroid therapy lowered plasma arginine vasopressin to normal in dehydrated patients. A normal diuretic response to hydration was accompanied by a fall in plasma arginine vasopressin level to zero in steroid-treated patients. In this study, the results suggested that hypersecretion of arginine vasopressin may have played an important role in the abnormal water metabolism of adrenocorticotropin deficiency, and that glucosteroids promoted normal water diuresis by inhibiting the secretion of arginine vasopressin from the neurohypophysis.

Hypothyroidism can cause hyponatraemia. Montenegro recently reported a study of serum electrolytes concentration and glomerular filtration rate before and after thyroid replacement therapy in 41 patients with hypothyroidism [9]. The authors observed that creatinine clearance was slighty decreased in all and that the decrease was more noticeable in the elderly. Hyponatraemia was found more often in patients with elevated serum creatinine levels than in those with normal serum creatinine levels. All these defects were corrected by treatment with thyroid hormone. Hypothyroid patients have a diminished ability to excrete free water, fail to achieve maximum urine dilution, and show delayed excretion of a water load [10]. The correlation between plasma arginine vasopressin levels and the capacity to excrete a water load is weak [11].

Our patient had an acute onset of hypothyroidism and severe adrenocorticotropin deficiency which can explain both hyponatraemia and inappropriate secretion of antidiuretic hormone. The sodium concentration initially was corrected by water deprivation. After 6 months of hormonal substitution, the sodium concentration remained normal without any water deprivation.

Whereas post-partum hyponatraemia is not a uncommon disorder secondary to surgical procedure or inadequate rehydration, hyponatraemia secondary to panhypopituitarisum should be suspected if severe blood loss occurred during delivery.



   References
 Top
 Introduction
 Case
 Discussion
 References
 

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Received for publication: 19. 4.99
Accepted in revised form: 25. 5.99





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