Anterior pituitary hormone dysfunction among individuals with complete heart block requiring pacemaker

Abstract

Background & objectives Neuronal hypoxia associated with conditions like traumatic brain injury and cardiac tachyarrhythmia has been implicated in causing hypopituitarism. Individuals with complete heart block (CHB) may be predisposed to develop anterior pituitary hormone dysfunction in the long term. The objective of this study was to investigate anterior pituitary hormone functions in individuals after CHB. Methods This prospective cohort study included 30 individuals (21 men and 9 women) with CHB requiring pacemaker implantation, who were evaluated at admission and then at a mean follow up of 12.4 ± 2.2 months to look for development of any degree of hypopituitarism. In addition to the measurement of hormones like follicle-stimulating hormone (FSH), luteinising hormone (LH), thyroid stimulating hormone (TSH), total tetra iodothyronines (TT4), free tetraiodothyronines (FT4), cortisol, insulin-like growth factor-1 (IGF-1), testosterone and estradiol, a fixed-dose glucagon stimulation test (GST) was performed to assess growth hormone (GH) and adrenocorticotrophic hormone (ACTH) axis. Results The mean age of the participants was 64.9 ± 11.3 yr. At follow up evaluation, 17 (56.7%) had low serum IGF-1, and among them, seven (23%) had growth hormone deficiency (GHD) (peak GH <1.0 ng/ml after GST). Six participants (20%) had ACTH deficiency (peak cortisol <9 ug/dl after GST) and one had TSH deficiency. None had prolactin (PRL) or gonadotropin deficiency. Overall, hormone deficiencies were observed in nine patients (30%). Interpretation & conclusions This pilot study detected loss of anterior pituitary hormones in a significant number of individuals of CHB at 12 months follow up. Unrecognised hypopituitarism may have resulted in significant morbidity and mortality in these individuals.

Keywords: Arrhythmia; growth hormone deficiency; heart block; hypopituitarism; pituitary.

Figure.

PERT chart showing study design and flow (mean follow up 12.4 ± 2.2 months). PERT, program evaluation and review technique; TSH, thyroid stimulating hormone; TT3, total tri-iodothyronine; FT3, free tri-iodothyronine; TT4, total tetra iodothyronines; FT4, free tetraiodothyronines; LH, luteinising hormone; FSH, follicle stimulating hormone; IGF-1, insulin-like growth factor-1; GH, growth hormone; CHB, complete heart block.