Familial Hyperaldosteronism Type I (FH-I): A Patient Guide

Familial Hyperaldosteronism Type I (FH-I), often referred to as Glucocorticoid-Remediable Aldosteronism (GRA), is a rare genetic condition that causes the body to produce an excessive amount of the hormone aldosterone ^[1]. This overproduction is not caused by lifestyle factors or diet, but by a specific biological error where two genes on chromosome 8—CYP11B1 and CYP11B2—become fused together to create a “chimeric” or hybrid gene ^[2]. This new gene is like a car with the body of one model and the engine of another: it produces aldosterone but is incorrectly controlled by the “on-switch” for cortisol, a hormone regulated by the brain’s daily rhythms and stress signals ^[3].

Because the brain constantly releases pulses of ACTH (adrenocorticotropic hormone) to maintain normal daily cortisol levels, normal ACTH signals inappropriately drive the hybrid gene to flood the body with aldosterone ^[4][1]. This excess hormone tells the kidneys to hold onto salt and water while losing potassium, which can lead to severe high blood pressure that begins much earlier than expected ^[1]. While many people do not develop hypertension until middle age, those with FH-I are often diagnosed in childhood or as young adults, frequently before the age of 20 ^[5]. It is important to note that this high blood pressure is often completely asymptomatic, so diagnosis relies heavily on screening and clinical evaluation rather than waiting for symptoms.

Early detection is essential because the constant pressure from excess aldosterone can put significant strain on the cardiovascular system ^[6]. If left unmanaged, this hormone-driven hypertension can lead to premature complications such as thickening of the heart muscle (left ventricular hypertrophy), eye damage, or an increased risk of early stroke ^[6][7]. Recognizing these risks early allows families and their doctors to implement a proactive monitoring plan to protect long-term health ^[8].

Fortunately, the treatment for FH-I directly targets this mechanism ^[9]. By using low doses of medications called glucocorticoids, doctors can gently lower the brain’s ACTH signal, which in turn suppresses the chimeric gene’s abnormal aldosterone production ^[1][10]. While this treatment does not repair or remove the inherited fusion gene—and therapy is often required long-term—it effectively controls the disease process. With a precise diagnosis and a care team focused on balancing these medications with regular surveillance, you or your child can effectively manage the condition ^[8].