A large amount of complex hormone associated processes occurring continuously in the human organism is necessary to maintain homeostasis in response to various internal and external conditions. In the same time, as the hormones use the bloodstream as their transmission medium, it is essential that their expression is strictly controlled to maintain their activity only when it is required. Because of that, the endocrine system evolved complex, self-regulating machinery that allows for precise signalling to the glands to initiate hormone expression, as well as equally quick negative feedback in the moment of reaching the optimal blood hormone concentration. The pituitary gland serves as the true endocrine part of that system, expressing a range of hormones that mostly serve as regulators of sub-systems serving different functions, scattered around organisms. The hypothalamus is the neuroendocrine part of the hypothalamic-pituitary axis, meaning it integrates the neuronal and hormonal signals, effectively linking the nervous and endocrine systems. The processes of hypothalamus and pituitary development share some significant similarities, which is unsurprising considering their close association and anatomical proximity at the base of the brain. Arising in highly overlapping developmental timeframes, they are both initially patterned by the gradients of extrinsic signalling molecules. After the initial lineage commitment, in both of those structures, intrinsic factors expressed by the distinct cell populations sustain the morphogenesis to result in a final complexly patterned structure. In this short review, the processes of the pituitary and hypothalamus development are described, with the most important factors driving them discussed.
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