Hypothalamus and Pituitary Gland Lecture 2022 PDF

HYPOTHALAMUS AND PITUITARY GLAND Dr. Kelly Roballo LEARNING OBJECTIVES 1 2 3 4 Differentiate between the anterior and posterior pituitary in terms of relationship with the hypothalamus. Differentiate the release of hormones from the anterior vs. posterior pituitary. Describe the role of hy...

HYPOTHALAMUS AND PITUITARY GLAND Dr. Kelly Roballo LEARNING OBJECTIVES 1 2 3 4 Differentiate between the anterior and posterior pituitary in terms of relationship with the hypothalamus. Differentiate the release of hormones from the anterior vs. posterior pituitary. Describe the role of hypothalamic releasing hormones in relation to the anterior pituitary. List and explain the function of the pituitary hormones. THE PITUITARY GLAND Adenohypophysis Neurohypophysis HYPOTHALAMUS AND THE PITUITARY GLAND • Hypothalamus and Pituitary work together to control many of the body’s endocrine functions. • Controls growth, milk production, osmoregulation. • Hypothalamus controls the pituitary via both neural and hormonal mechanisms. • Pituitary is connected to the hypothalamus by a structure named the infundibulum. INTERACTION BETWEEN THE HYPOTHALAMUS AND POSTERIOR PITUITARY • The posterior pituitary may be thought of as a collections of axons whose cell bodies are located within the hypothalamus. • The hormones of the posterior pituitary are released by neurons. • Hormones are synthesized in cell bodies located within the hypothalamus à hormones are then transported down axons via neurosecretory vesiclesà vesicles are stored at nerve terminals until they are released into the circulation INTERACTION BETWEEN THE HYPOTHALAMUS AND ANTERIOR PITUITARY u Contains both neural and endocrine communications. u Hypothalamus utilizes releasing hormones to facilitate communication with the anterior pituitary. u Releasing hormones act on endocrine cells within the anterior pituitary triggering release of hormones into the blood. PITUITARY HORMONES ANTERIOR (ADENOHYPOPHYSIS) POSTERIOR (NEUROHYPOPHYSIS) • Thyroid Stimulating Hormone (TSH) • Follicle Stimulating Hormone (FSH) • Luteinizing Hormone (LH) • Adrenocorticotrophic Hormone (ACTH) • Growth Hormone • Prolactin • Anti-diuretic Hormone (ADH aka vasopressin) • Oxytocin ANTERIOR PITUITARY u Anterior lobe is derived from the primitive foregut u Anterior pituitary is a collection of endocrine cells u Hypothalamic-hypophysial portal blood vessels u Provide majority of blood supply to the anterior pituitary u Hypothalamic hormones delivered to anterior pituitary directly and in high concentrations and never enter systemic cirulation u Anterior pituitary cells are the only cells exposed to high concentrations of hypothalamic hormones ANTERIOR PITUITARY Releasing hormone from hypothalamus Target cells of anterior pituitary Hormone released by anterior pituitary Growth Hormone Releasing Hormone (GHRH) Somatotrophs Growth hormone Thyroid Releasing Hormone (TRH) Thyrotrophs TSH Corticotropin Releasing Hormone (CRH) Corticotrophs ACTH Gonadotropin Releasing Hormone (GnRH) Gonadtrophs FSH and LH N/A Lactotrophs Prolactin THYROID STIMULATING HORMONE (TSH) u Glycoprotein hormone u Acts on follicular cells in the thyroid, leading to secretion of thyroid hormones u Triiodothyronine (T3) u Thyroxine (T4) u Clinical relevance: u TSH is measured to give clinicians information about how the thyroid gland is working u This is based off the concept of feedback u High TSH = Hypothyroid u Low TSH = Hyperthyoid FOLLICLE STIMULATING HORMONE (FSH) AND LUTEINIZING HORMONE (LH) u Follicle Stimulating Hormone u Acts on ovarian follicular cells to make estrogens and progestins. Controls menstrual cycle and stimulates growth of eggs within the ovary u Act on Sertoli cells of the testicles to make testosterone and induce spermatogenesis u Luteinizing Hormone u Female: LH surge is responsible for ovulation, LH also helps to maintain pregnancy if fertilization occurs. u Male: Stimulate Leydig cells to produce testosterone u LH is VERY important in controlling puberty for both males and females ADRENOCORTICOTROPHIC HORMONE (ACTH) • Acts of adrenal cortex to stimulate the production of corticosteroids (Cortisol) • Cortisol is important in: • Responding to stress • Regulation of blood sugar • Maintenance of blood pressure • Regulation of metabolism • ACTH testing can help with the diagnosis of Cushing’s (too much ACTH production)and Addison disease (low cortisol production) GROWTH HORMONE • Stimulates productions of Insulin-like growth factor from the liver (and other non endocrine tissues). • Stimulates growth in children • Also increases anabolic action of cells • Acromegaly (after puberty) • Pituitary produces too much growth hormone in adulthood (too much in childhood leads to gigantism) • Bones increase in size • Affected people have increased bone thickness in hands and face • Treat with somatostatin analogues (e.g., octreotide) GROWTH HORMONE PROLACTIN u Acts on mammary glands to initiate and maintain milk production u Inhibited by dopamine u Hyperprolactinemia and typical antipsychotics u Ex: Risperidone u These drugs block the inhibition of dopamine and lead to a rise in prolactin levels u S/Sx: u Females: Infertility, irregular menstruation, lactation (galactorrhea) u Males: Breast growth (gynecomastia), Lactation, infertility POSTERIOR PITUITARY u Derived from neural tissue, hence the name “Neurohypophysis” u Secretes two peptide hormones: u Antidiuretic hormone (ADH): acts on kidney tubules u Oxytocin: acts on breasts and uterus ANTIDIURETIC HORMONE • Acts on collecting ducts of kidneys to reabsorb water. OXYTOCIN • Acts on uterus, causing contractions during labor • Also acts on mammary glands to aide in ejection of milk • Pitocin (oxytocin) • Injected to induce or aide labor • Also used to treat post-partum hemorrhage (PPH): oxytocin causes uterus to contract leading to tamponade of the uterine blood vessels. PITUITARY ADENOMA u Neoplasms within the pituitary gland u Most tumors are benign with resolution of symptoms after resection u S/Sx: u Related to mass effect (compression/interference with surrounding structures) u Visual defects (compression of optic nerve) u Headache u CSF rhinorrhea if extension into sphenoid sinus u S/Sx related to excessive hormone release THANK YOU