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Sjögren’s syndrome is a systemic autoimmune disease characterised by lymphocytic infiltration of exocrine glands accompanied by a variety of extraglandular manifestations.1 Endocrinological manifestations, however, are infrequently encountered with the exception of autoimmune thyroiditis.2 3
A 76 year old woman was brought to the emergency room for syncope. She was diagnosed with bradycardia resulting from atrioventricular block with a ventricular rhythm of 30 bpm and a VVI pacemaker was placed to control the life threatening bradycardia. Her complaints were chronic fatigue, cold intolerance, decreased appetite, xerostomia, and dry eyes over the past five months. There was no history of arrythmias nor was there any hint that an overdose of medication caused the atrioventricular conduction disturbance. She gave birth to three children and menstruated until age 53 ruling out Sheehan’s syndrome as a cause for hypopituitarism. Physical examination demonstrated decreased skin and nipple pigmentation, a hoarse voice, and loss of axillary and pubic hair.
Laboratory tests showed increased erythrocyte sedimentation rate of 66 mm 1st h, normochromic and normocytic anaemia, hyponatraemia, and hyperimmunglobulinaemia. The leucocyte count was not raised, with a normal white cell differential and normal serum C reactive protein, ruling out acute inflammation.
As the patient’s complaints and physical findings pointed towards a complex endocrine disorder, several tests were conducted. Serum concentrations of free thyroxine (7.1 pmol/l (normal 9.0–24.5)), free triiodothyronine (4.8 pmol/l (normal 3.4–7.00)), thyrotropin basal (1.1 mU/l (normal 0.17–2.9)), and basal prolactin (2.1 ng/ml (normal 2–20) were near normal, whereas the stimulation with thyrotropin releasing hormone was blunted for thyrotropin (1.76 mU/l) and prolactin (2.3 ng/ml), indicating a final insufficiency of these regulatory pathways. Furthermore, basal serum cortisol and adrenocorticotropin concentrations were 4.06 μg/dl (normal 4.4–17.4) and 5.7 pg/ml (normal 7–74) but failed to rise upon appropriate stimulation upon corticotropin releasing hormone testing. Basal serum concentrations of luteinising hormone (< 0.5 mIU/ml (normal 10.8–61)) and follicle stimulating hormone (0.9 mIU/ml (normal 35–151)) were found to be diminished. The serum concentration of growth hormone (0.3 μIU/ml (normal <1–10)) also did not respond to stimulation with arginine. The plasma vasopressin was slightly increased (7.1 pg/ml (normal 1.5–6)). These findings are consistent with hypopituitarism accompanied by inappropriate secretion of vasopressin (SIADH). Autoantibodies against thyroid microsomal antigen, thyroglobulin, and TSH receptor were not detected. However, increased antibody titres against smooth muscle (1:8) and against parietal cells (1:4) were indicative of autoimmune hypophysitis.6 Computed tomography did not show any pituitary abnormalities. Because of the implanted pacemaker, magnetic resonance imaging could not be performed.
The diagnosis of Sjögren’s syndrome was established by xerostomia, keratoconjunctivitis sicca, positive Schirmer test (right 3 mm/5 min, left 2 mm/5 min) positive ANA (1:64) with anti-60kD Ro(SS-A)/La(SS-B) antibodies meeting the European study group classification criteria.7 A salivary gland biopsy was considered but not performed because the patient did not give her consent. Rheumatoid factor was not detectable.
The patient was given a substitution regimen of 7.5 mg/d prednisolone and 75 μg/d L-thyroxine and 400 mg/d hydroxychloroquine for Sjögren’s syndrome. Her symptoms improved after four weeks. Her electrocardiographic readings returned to a normal sinus rhythm. Hydroxychloroquine was discontinued later because it did not further improve the clinical symptoms.
Interactions between the neuroendocrine and immune system are increasingly appreciated.8 Our case report suggests that the pituitary gland may be another site of lymphocyte infiltration in Sjögren’s syndrome. This could eventually cause pituitary dysfunction, possibly because of local immune cell mediated tissue injury or autoantibodies, or both. Both autoantibodies in Sjögren’s syndrome9 and hypothyroidism10 resulting from hypopituitarism have been described to cause heart blocks. The condition that was predominant in our case cannot be determined.
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