8138 Pituitary Stalk Interruption Syndrome (PSIS) in a patient with Isolated Hypogonadotropic Hypogonadism

Abstract Disclosure: A. Thomson: None. R. Osman: None. Pituitary Stalk Interruption Syndrome in a Patient with Isolated Hypogonadotropic Hypogonadism Pituitary Stalk Interruption syndrome (PSIS) is a rare cause of hypopituitarism, characterized by a radiologic constellation of thin or interrupted pituitary stalk, hypoplasia, or aplasia of the anterior lobe and with the presence of an ectopic posterior pituitary (EPP). It is most commonly associated with isolated growth hormone deficiency (IGHD) and is often diagnosed in childhood. We present one case of a patient with isolated hypogonadotropic hypogonadism in adulthood, subsequently found to have an PSIS on MRI. A 45 year old male patient presented to our clinic with hypogonadism. He gradually started developing decreasing libido, fatigue, and loss of erections. He had normal puberty and childhood growth, and has fathered one child. He denied history of anosmia or visual symptoms. Subsequent hormonal testing showed: morning Total Testosterone: 145 ng/dl (normal 264-916 ng/dl), Free testosterone 1.5 pg/ml (normal 6.8-21.5 pg/ml), LH 1.1 mIU/ml (normal 1.7-8.6 mIU/ml) and FSH of 3.6 mIU/ml (normal 1.5-12.4 mIU/ml). Prolactin was minimally elevated at 21 ng/ml (normal 4.0 - 15.2 ng/ml). Thyroid, IGF-1, cortisol, and ferritin levels were within normal limits. Repeat levels showed similar findings. He denied ever taking any form of exogenous testosterone. His pituitary MRI revealed a small volume of anterior pituitary tissue, measuring 0.2cm x 0.7cm x 0.7cm, without discrete pituitary adenoma, a hypoplastic midline stalk measuring 1.3 mm in AP diameter (nl 2-3 mm), with a T1 hyperintense nodularity measuring 0.6cm x 0.4cm along the posterior aspect of the sella turcica consistent with EPP. No additional structural abnormality or any mass lesions were identified. He was subsequently started on replacement testosterone therapy and his symptoms resolved. PSIS usually presents in childhood with IGHD. Patients may have other pituitary hormone deficiencies and congenital central nervous system defects, although panhypopituitarism is rare. There have been reports in children with delayed puberty and isolated hypogonadotropic hypogonadism who have been found to have PSIS. Only one othercase of an adult female patient exhibiting hypogonadotropic hypogonadism as the only manifestation of PSIS has been documented in the literature. Our case highlights the potential for an adult male to present later in life with hypogonadotropic hypogonadism as a manifestation of PSIS. The marginally elevated prolactin level may be due to lack of inhibition of hypothalamic dopamine on lactotroph cells within the pituitary caused by the EPP, although it is doubtful that this has clinical significance. This is a rare presentation of PSIS, clinicians should be mindful ofthis radiological constellation and the potential for isolated hypogonadotropic hypogonadism presenting unusually in the adulthood. Presentation: 6/3/2024