Segmental MRI Pituitary and Hypothalamus Volumes post Fontan: An analysis of the Australian and New Zealand Fontan Registry.

Abstract

Objective: Short stature, central hypothyroidism and infertility are common in those with a Fontan circulation. Given that the Fontan circulation often results in hepatic portal venous congestion, we hypothesize that the hypothalamic-pituitary portal circulation is also affected, contributing to subsequent hypothalamic-pituitary axis dysfunction. Methods: MRI data from the Australian and New Zealand Fontan Registry (86 cases) was compared to 86 age- and sex- matched normal published controls. Total pituitary volumes (both anterior and posterior glands) were measured using a manual tracing segmentation method, and hypothalamic (and subunit) volumes using an automated segmentation tool. Measured gland volume was normalized to total brain volumes. A generalized linear model was used for statistical analysis. Results: Normalized total pituitary volumes (nTPV) were increased in Fontan patients compared to controls (p <0.0001), due to an increase in anterior pituitary volumes (nAPV) (p <0.0001), with no difference in normalized posterior pituitary volumes (p = 0.7). Furthermore, normalized anterior and tubular hypothalamic subunit groups) were increased in Fontan patients compared to the controls (p <0.01 and p <0.0001, respectively). The time between Fontan and MRI was positively related to nTPV, nAPV and bilateral hypothalamic volumes. nTPV increased with age, and the increase in nAPV was greater in Fontan patients. Conclusions: Segmental MRI Pituitary and Hypothalamus volumes post Fontan are increased and are related to the time since Fontan procedure. These findings are consistent with venous congestion of the anterior hypothalamic-pituitary portal venous system and may explain the high frequency of endocrine dysfunction in this patient group.