The pituitary stem is a median organ normally measuring between 1 and 1.5 mm thick. It is said to be thickened when its diameter varies between 2.5 and 3 mm [1]. This anomaly, increasingly encountered on pituitary magnetic resonance imaging (MRI) since its development, is found in various pathologies including diabetes insipidus which is an inaugural sign, inflammatory, infectious, infiltrative, or tumor pathologies. The etiological diagnosis being uncertain, monitoring of lesions or histological evidence, is necessary to determine with certainty the cause [2],[3].

We report the case of a 49-year-old patient. Mother of two children, widow without past history (ATCD), in whom the sudden installation of polyuria and polydipsia dating back about 26 months, required a consultation in endocrinology where she was hospitalized.

The clinical examination found an obese patient with a body mass index (BMI) of 41 kg/m², normal cardiovascular examination with blood pressure (BP) at 130/80, heart rate (FC) at 108 bpm, and electrocardiogram (ECG) without particularity. She had a severe polyuro-polydipsic syndrome with urination greater than 8 liters (L) estimated at 10 L/day (d) and 6 nocturnal awakenings. During hospitalization, she benefited from a 6 hors water restriction test, with the realization of a urinary ionogram which made it possible to highlight a urinary osmolarity of less than 700 mosm/L. A therapeutic test (anti-diuretic hormone = DHA), Minirin 120 ug spray 1×/d for 72 hours improved her syndrome, with a regression of urination (3 L/d and a night awakening).

An etiological survey was carried out. The examination of the pituitary axes, including the determination of thyrotropic hormones (TRH=Thyrotripin-liberin=thyrotripin-releasing hormone, TSH = TSH=thyroid-stimulating hormone, T3, T4, and gonadotropic hormones (FSH=follicle-stimulating hormone, LH=luteinizing hormone was without abnormality.

Biologically, there was hypochromic microcytic anemia with a complete blood count (SN) a hemoglobin level of 5.9 g/100 mL per hematocrit at 23%, the mean blood cell volume (GMV) at 59.7 u³.

The positive inflammatory balance with a sedimentation rate (VS) accelerated to (1 hour = 58 mn; 2 hour = 100 mn), the reactive protein C (CRP) increased to 14.23 mg/L.

Biochemistry returned to normal blood sugar at 0.91, hemoglobin glycated (HbA1C) normal at 5.1, ferritin 6.18 ng/mL.

The search for Koch's bacillus (BK) in the sputum had returned to normal.

Cytobacteriological examination and urinary biochemistry were normal. Histological examination of the biopsy fragment of the salivary gland showed a discrete chronic non-specific sialadenitis without amyloid and granuloma deposition.

The radiological assessment on abdominal and transthoracic ultrasound found no abnormalities. X-ray of long bones was normal. The chest X-ray found an interstitial syndrome with mediastinal lymphadenopathy.

A pituitary magnetic resonance imaging (MRI) performed found a thickened pituitary rod measuring 3 mm without interruption syndrome (Figure 1).

Imaging is essential in the etiological assessment of a large pituitary stem discovered during diabetes insipidus. Various pathologies among other inflammatory, infectious, infiltrative, or tumorous can be discussed in adults with a higher frequency for inflammatory or granulomatous diseases.

Sarcoidosis in the first line was evoked in our patient, in front of inflammatory biological signs, and pulmonary involvement with mediastinal lymphadenopathy. The absence of epithelioid granuloma in salivary gland biopsy (BGSA) on histological examination, allowed us to eliminate it.

Erdheim-Chester disease and hystiocytosis were also evoked in front of pulmonary signs, but eliminated in front of the absence of bone lesions on X-ray of long bones. A tuberculous origin has been evoked in front of the pulmonary signs, but refuted with the absence of BK in the sputum.

Faced with the absence of bundles of arguments eliminating the aforementioned etiologies, the diagnosis adopted in our patient is lymphocytic pituitary gland (HL) [1].

Lymphocytic pituitary gland (HL) is an autoimmune endocrinopathy of relatively recent individualization, since its first description nearly 40 years ago. It is an essentially female autoimmune pathology that most often reveals itself during pregnancy and the immediate postpartum. It can also occur years later. According to the literature, this still poorly known pathogenesis is related to lymphocytic infiltration of the pituitary gland. Hormonal deficiencies are common (65%), including ACTH (adrenocorticotrophic hormone) deficiency. In common practice, the determination of anterior pituitary antibodies is not useful for diagnosis, given their low sensitivities, since in 25% of cases associated with other autoimmune diseases [1],[4].

Anyway, the difficulty in asserting with certainty this etiology without histological proof (biopsy-neurosurgical excision), due to the slow evolution of certain pathologies delaying their clinical manifestation [1],[4].

The patient was finally put on replacement therapy, in order to lower the polyuro-polydipsic syndrome and limit nocturnal awakenings; Minirin 60 ug in spray 2×/d. This made it possible to improve her quality of life with the regression of his symptomatology. However, regular monitoring of lesions by pituitary MRI is required.

The discovery of a large pituitary stem on pituitary MRI, in the context of diabetes insipidus, raises a wide diagnostic range that must be guided by clinical and biological data.