FUNCTIONAL ANATOMY AND PHYSIOPATHOLOGY OF HYPOTHALAMUS AND ADENOHYPOPHISIS

1. FUNCTIONAL ANATOMY AND PHYSIOPATHOLOGY OF HYPOTHALAMUS AND ADENOHYPOPHISIS PHYSIOTHERAPY IN ENDOCRINE PATHOLOGY

2. Outline and objectives of the course

3. HYPOTHALAMUS - STRUCTURE

4. OVERVIEW • Located inferior to the talamus • Represents the ventral region of the midbrain • Center of homeostasis

5. GENERAL PRESENTATION • The hypothalamus (from Greek ὑποθαλαμος = under the thalamus) is a region of the mammalianbrain located below the thalamus, forming the major portion of the ventral region of the diencephalon and functioning to regulate certain metabolic processes and other autonomic activities. • The hypothalamus links the nervous system to the endocrine system via the pituitary gland, also known as the "master gland," by synthesizing and secreting neurohormones, often called releasing hormones, as needed that control the secretion of hormones from the anterior pituitary gland— among them, gonadotropin-releasing hormone (GnRH). The neurons that secrete GnRH are linked to the limbic system, which is primarily involved in the control of emotions and sexual activity. The hypothalamus also controls body temperature, hunger, thirst, and circadian cycles.

6. GENERAL PRESENTATION • The hypothalamus co-ordinates many seasonal and circadian rhythms, complex patterns of neuroendocrine outputs, complex homeostatic mechanisms, and many important stereotyped behaviours. The hypothalamus must therefore respond to many different signals, some of which are generated externally and some internally. The hypothalamus is thus richly connected with many parts of the CNS, including the brainstem reticular formation and autonomic zones, the limbic forebrain (particularly the amygdala, septum, diagonal band of Broca, and the olfactory bulbs, and the cerebral cortex).

7. FUNCTION • The hypothalamus is responsive to: • Light: daylength and photoperiod for generating circadian and seasonal rhythms • Olfactory stimuli, including pheromones • Steroids, including gonadal steroids and corticosteroids • Neurally transmitted information arising in particular from the heart, the stomach, and the reproductive tract • Autonomic inputs • Blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc • Stress • Invading microorganisms by increasing body temperature, resetting the bodys thermostat upward.

8. The hypothalamus is a very complex region, and even small nuclei within the hypothalamus are involved in many different functions. The paraventricular nucleus contains oxytocin and vasopressin neurons which project to the posterior pituitary, but also contains neurons that regulate ACTH and TSH secretion (which project to the anterior pituitary), gastric reflexes, maternal behavior, blood pressure, feeding, immune responses, and temperature.

9. Hypothalamic nuclei - Lateral Area Anterior Lateral preoptic nucleus Lateral nucleusPart of supraoptic nucleus Tuberal Lateral nucleusLateral tuberal nuclei Posterior Lateral nucleus • Medial Area • Anterior • Medial preoptic nucleusSupraoptic nucleusParaventricular nucleusAnterior nucleusSuprachiasmatic nucleus • Tuberal • Dorsomedial nucleusVentromedial nucleusArcuate nucleus • Posterior • Mammillary nuclei (part of mammillary bodies)Posterior nucleus

10. Hormones of the hypothalamus • Corticotropin-releasing hormone (CRH) • Dopamine • Gonadotropin-releasing hormone (GnRH) • Growth hormone releasing hormone (GHRH) • Somatostatin • Thyrotropin-releasing hormone (TRH) • Hypocreatin • Antidiuretic Hormone (ADH)

11. HT role in obesity • An important aspect of hypothalamic autonomic control with regard to the endocrine system is the control of food intake. The effects of obesity on endocrine function can be widespread and endocrine abnormalities can cause obesity. A number of hormones play central roles in the control of food intake

12. Measures of obesity • Three main experimental measures of fat mass in man have been used for many years. They require the determination of body density, water or potassium content and the assumption that the body composition can be divided into fat and fat-free or lean body mass with certain characteristics. These techniques are relatively costly, time-consuming and do not give information on the distribution of the fat. • Techniques such as bioelectrical impedance rely on the fact that fat is not as good an electrical conductor as lean body mass. It is cheap but also does not allow an assessment of the distribution of the fat mass. • Imaging techniques such as CT or MR allow the determination of fat from a number of tomographic 'slices' of the body. The distribution of the fat mass can be calculated. • Simple anthropomorphic measurements such as height and weight allow the calculation of body mass index (BMI), whilst calipers can be used to measure subcutaneous fat. • BMI = body weight (in kg)/height2 (in m) • Waist/hip circumference * = ratio of waist circumference to that of the hips

13. HIPOPHYSIS (pituitary gland) • O,5-0,8 G • anterior pituitary (adenohypophysis) • posterior pituitary (neurohypophysis) • Regulated by hypothalamus – providing anatomical and physiological connections between nervous and endocrine system

14. ADENOHYPOPHYSIS Connected with the hypothalamus via the hypophyseal portal system NEUROHYPOPHYSIS Connected with the hypothalamus via the hypophyseal tract

15. HORMONES OF THE ADENOHYPOPHISIS • Somatotropin (growth hormone) • Prolactin • Gonadotropines: follicle-stimulating hormone (FSH); luteinizing hormone (LH) • Thyroid stimulating hormone (TSH) • Adrenocorticotropic hormone (ACTH)

16. Thyrotropin • Stimulates the thyroid gland to synthetize and secrete its hormones (triiodothyronine – T3; thyroxine – T4) Regulation by negative feedback ( high concentration of T3 and T4 in blood)

17. Gonadotropines (FSH, LH) • FSH stimulates the maturation of an ovum each month during a female reproductive years • Stimulates maturation of sperm in males • Stimulates production of estrogen hormones • Regulation by negative feedback ( high concentration of estrogensin blood)

18. LH • Stimulates ovulation and causes follicular cells to produce progesterone which stimulates nidation and mammary gland development • In males stimulates development of interstitial cells (Leydig) of testis; stimulates production of testosterone

19. Somatotropin • Acts directly on some cells to stimulate growth • Acts indirectly on others to release proteins (insulin like growth factor I) • Promotes calcium absorbtion from intestine • Works with insulin and thyroid hormones to promote collagen synthesis

20. Increase the rate at wich cells take up aminoacids and use them to synthetise proteins • Stimulate free fatty acid release from fat cells and glycogen breakdown in the liver • Stimulate growth to adult size

21. Bone and muscle loss associated with reduced strength in aging may be due to declining GH after age 50. • At age 30 – body mass: 10% bone, 30% muscle, 20% fatty tissue • At age 75 - body mass: 8% bone, 15% muscle, 40% fatty tissue

22. Corticotropin(ACTH) • Acts on the cortex of the adrenal gland to regulate synthesis and secretion of several of its hormones, especially glucocorticoids • Glucocorticoids stimulate the release of fatty acids and glucose into the blood and help the body to resist stress and inflamation Regulation by negative feedback ( high concentration of cortisol in blood)

23. Prolactin • Stimulates milk secretion in mammary glands previously prepared for milk production by other hormones – estradiol, progesterone, corticosteroids, insulin

24. Beta-lipoprotein • Has been isolated from the anterior pituitary gland • Endorphins and enkefalins can be made from it in the anterior pituitary or in the brain directly

25. Melanocyte stimulating hormone • Secreted in small quantities by the intermediate lobe of pituitary gland • Role in skin pigmentation

26. Regulation of the adenohypophyseal hormones • By neurohormones secreted by hypothalamus (releasind and inhibiting) • Tropic hormones from the anterior pituitary regulate other glands such as the thyroid, adrenal cortex, gonads • Hormones from these glands act by negative feedback to inhibit the release of both tropic and hypothalamic hormones • Neural signals elicited by sexual arousal, stress, anxiety, trauma, variations in the light-dark cycle and the sucking of a breast-fed infant also regualte hypothalamus hormones

27. Hypothalamic hormones that regulate secretion of adenoHY

28. Hormones of the neurohypophysis • 2 chemically similar peptide hormones, ocytocin and antidiuretic hormone are called neurosecretions because are synthetised in hypotalamic neurons and stored in the neuroHY • When action potentials causes their release from axons they enter the blood and act as hormones.

29. Oxytocin • Stimulates contraction of smooth muscle in the uterus and the contractile cells around mammary gland ducts • Is relased during sexual intercourse, labor, lactation

30. Antidiuretic hormone (ADH) • Also called vasopresine • Prevents excess water loss in urine • In high concentrations constricts blood vessels • Decreases osmotic pressure and the urine volume • Increases the blood volume

31. Pituitary disoders

32. Reminder

33. Reminder

34. REFERENCES • Avramescu ET, Rusu L., Ciupeanu – Calugaru D., 2005, Human Anatomy, Universitaria Publishing House, Craiova, • Bello M., Testing the effects of growth hormone releasing hormone, Research Resources 9, no 10:1, 1985 • Creager J., 1992, Wm. C. Brown Publisher • Lechan, R., Neuroendocrinology of pituitary hormone regulation, Endocrinology and Metabolism Clinics 16, no 3:475, 1987