MON-455 Prevalence of Hormonal Deficiencies in Nonfunctional Pituitary Microlesions: Does Size Matter?

Abstract

Objective: Non-functional pituitary micro-lesions (<1cm in size), owing to their small size, have classically not been thought to cause hormonal deficiencies. We postulated that the frequency of hormonal deficits (in particular of gonadotrophic hormones) in small pituitary lesions is high. Furthermore, we speculated that rates of hormonal deficits may not correlate with size of lesion. Methods: We studied consecutive patients who were referred to a single Pituitary Center between February, 2014 and July, 2018. Inclusion criteria included the presence of a pituitary lesions measuring <1cm, and the absence of hormonal hypersecretion. Patients were excluded who, a) did not complete hormonal work up, b) did not have size of lesion specified on imaging, and c) females who were on oral contraceptive pills. Results: A total of 69 patients (42 men and 27 women) met criteria for the study. The most common presenting symptoms were erectile dysfunction/low libido or oligomenorrhea/amenorrhea affecting 36% of men and 19% of women respectively. Of the total population, 55% were found to have hormonal deficiencies in at least 1 axis. Men had higher rates of deficits with 76% affected, while women had deficiencies in 22% of the cases. The most common hormonal deficit was hypogonadotropic hypogonadism, affecting 64% of total men and 11% of women. The average age of men presenting with hypogonadism was 43 years. Following hypogonadism, men were affected by growth hormone deficiency (low IGF-1) in 9.5% of cases and central adrenal insufficiency in 2.4% of cases. Women, on the other hand, had central hypothyroidism 7.4% of the time and adrenal insufficiency 3.7% of the time. The mean size of lesion in patients with hormonal deficits was 4.76mm (median 5mm). Of patients who had a pituitary lesions smaller than 6mm, 54% of cases had hormonal deficits, compared to 58% of patient affected with lesions greater than 6mm in size (p>0.05). Discussion: The pathophysiology of hormonal loss caused by pituitary lesions is unknown but could be postulated to result from compressive damage. Size has been thought to be an important determinant of hormonal loss, with larger lesions causing significant deficits while those <6mm being less involved. The 2011 Endocrine Society guidelines for the evaluation of pituitary incidentalomas more strongly support testing for lesions 6-9 mm in size (1). In our study we found a significant proportion of patients with pituitary micro-lesions had hormonal deficits, even at 6 mm or less, in particular hypogonadotropic hypogonadism in young men. Furthermore, the size of the lesion did not appear to correlate with hormonal loss.