aivolisäkehypotalamuksen

Aivolisäkehypotalamus, often described in Finnish as the hypothalamic-pituitary axis, is a central endocrine system that links the brain to peripheral glands to regulate growth, metabolism, reproduction, and stress responses. The hypothalamus produces releasing and inhibiting hormones that control the anterior pituitary (adenohypophysis) via the hypothalamic-pituitary portal system. The posterior pituitary (neurohypophysis) stores and releases hormones produced by the hypothalamus, principally antidiuretic hormone (vasopressin) and oxytocin.

Structure and function: The anterior pituitary secretes ACTH, TSH, growth hormone (GH), prolactin, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). These hormones are regulated by hypothalamic factors such as corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GHRH), somatostatin, gonadotropin-releasing hormone (GnRH), and dopamine. The posterior pituitary releases vasopressin and oxytocin in response to neural signals. The axis operates mainly through negative feedback: cortisol, thyroid hormones, and sex steroids modulate hypothalamic and pituitary activity; circadian and stress-related inputs also influence secretion patterns.

Clinical relevance: Disturbances can arise from pituitary adenomas, leading to hormone excess (for example, GH in acromegaly, ACTH in Cushing’s disease, prolactin in prolactinomas) or deficiency (hypopituitarism). Posterior pituitary disorders include central diabetes insipidus due to ADH deficiency. Other conditions involve pregnancy-related pituitary changes, inflammation, or trauma. Diagnosis relies on hormone assays and magnetic resonance imaging; treatment ranges from hormone replacement and medical therapy to surgical or radiotherapeutic management of tumors.