In recent decades, dozens of genes that cause isolated and combined pituitary hormone deficiencies have been discovered. We will review the clinically relevant genes known to cause isolated and combined pituitary hormone deficiencies in humans. This review will address genetic causes of adrenocorticotropic hormone deficiency, thyroid stimulating hormone deficiency, growth hormone deficiency, hypogonadotropic hypogonadism, and diabetes insipidus. Additionally, we will discuss genetic causes of combined pituitary hormone deficiency, septo-optic dysplasia, holoprosencephaly, and multisystemic syndromes in which hypopituitarism is a significant component. With the widespread clinical availability of next generation sequencing and ongoing identification of new disease causing genes, genetic diagnoses are determined for increasing numbers of patients. With new insights into mechanisms of disease resulting from multiple gene interactions, an increasingly nuanced understanding of the underlying genetic etiology of pituitary hormone deficiencies is possible.