What is an endocrine gland?

1. What is an endocrine gland? • Secretary structure • Secretes hormone into interstitial fluid, then blood • Secretion rates are extremely low • All are highly vascularized

2. What is a hormone? • It is a chemical substance produced in the body that encourages growth or influences how the cells and tissues function. • Small molecule, protein, glycoprotein or lipid • Released into blood • Binds to specific receptors

3. Hormone Secretion Stimulus (another hormone, changes in blood chemistry or nerve stimuli) Endocrine Gland ----------------Hormone Hormone secretion Blood Binds to Receptor------------ Target cell Action

4. Pituitary Gland • Also called hypophysis, weighs 0.5 grams with dimension of • 10 x 13 x 6 mm • Lies within the cavity of sella-turcica and hangs inferior to hypothalamus. • -Releases 9 important peptide hormones • Hormones bind to membrane receptors • During embryogenesis hypophysis develops partly from oral tissue and partly from nerve tissue • The hypophysis actually consists of two glands: • - neurohypophysis (neural origin) and adenohypophysis (oral origin) Figure 18–6

5. Hypothalamus/pituitary gland

6. Hormones secreted by anterior pituitary gland • Human growth hormone (somatotrophs) • which promotes growth • Thyroid-stimulating hormone (thyrotrophs) • which regulates the endocrine function of the thyroid gland • Follicle-stimulating hormone; luteinizing hormone • They act synergistically in reproduction • Prolactin (lactotrophs). It stimulates the mammary glands to produce milk (lactation) • ACTH (adrenocorticotropic hormone). It effects are increased production and release of corticosteroids and cortisol from the adrenal cortex. • MSH (melanocyte-stimulating hormone). They stimulate the production and release of melanin

8. Neurohypophysis (= posterior pituary) • This neurosecretory material consists of two hormones made up of cyclic peptides. They are Antidiuretic hormone (ADH) and Oxytoxin. • ADH is released in response to increased tonicity in blood due to lose of water or increased salt absorption. • Thus it regulate osmotic balance of the blood Oxytocin • stimulate contraction of ducts and alveoli of mammary gland during nursing. • stimulates the contraction of smooth muscles of the uterus during copulation and delivery..

9. Posterior pituitary

10. Pineal Gland • It is a conical organ weighing about 120 mg that lies in posterior portion of roof of third ventricle (diencephalons) • Contains mostly pinealocytes and astrocytes: • synthesize hormone melatonin composed of peptides • The hormone involves in the inhibition of reproductive functions. • Protecting against damage by free radicals • Setting circadian rhythms (biorhythms) associated with cyclic environment and body.

11. Pancreas • Alpha Cells = The alpha cells secrete glucagon • Beta Cells = secrete insulin and amylin which functions as synergistic partner to insulin • Gamma Cells = secrete a polypeptide which reduces appetite • Delta Cells = secrete somatostatin / they work to reduce the rate at which food is absorbed from the contents of the intestine.

12. Adrenal Glands • Each adrenal gland is separated into two distinct structures, the adrenal cortex and medulla, both of which produce hormones. • The cortex mainly produces cortisol, aldosterone, and androgens, while the medulla chiefly produces epinephrine and norepinephrine. • 1)Cortisol = It increases blood pressure and blood sugar, and reduces immune responses. • 2)Aldosterone = increases the reabsorption of sodium and water and the release (secretion) of potassium in the kidneys. • 3)Androgen = stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. • 4)Epinephrine&Norepinephrine = When produced in the body it increases heart rate, contracts blood vessels and dilates air passages and participates in the "fight or flight" / norepinephrine has basically same as epinephrine, but it acts more locally.

14. Common endocrine disorders Diabetes • Currently, there are approximately 23 million Americans with diabetes and an additional 57 million Americans have pre-diabetes.  • Recent studies have found that controlling blood sugar helps prevent serious problems that can be caused by diabetes. These can include problems with the eyes, kidneys and nerves, which can lead to blindness, dialysis, or amputation. • Endocrinologists treat diabetes with diet and medications, including insulin. They also work closely with patients to control blood sugar and monitor them so they can prevent health problems. 

15. Thyroids • estimated that up to 10% of Americans have some sort of thyroid disease.  Patients with thyroid disorders often have problems with their energy levels. • Hyper thyroid- over production of thyroids hormone. • Hypo thyroid – underproduction of thyroids hormone. • Almost half of the population will have tiny thyroid nodules at some point in their livesbut, typically, these are not noticeable until they become large and affect normal thyroid size. Significant sized nodules, greater than a half inch across (about 1 centimeter), occur in about 5 percent of people.  • More than 90 percent of all thyroid nodules are not harmful or cancerous.  In fact, thyroid cancer is found in only 8% of men and 4% of women. 

16. Bone • Osteomalacia (rickets), which causes bones to soften, and osteoporosis are bone diseases that endocrinologists diagnose and treat. Osteoporosis is a disease that weakens your skeleton. • Endocrinologists treat other disorders that can affect bones, such as too much parathyroid hormone and long term use of steroids like prednisone.

17. Obesity and Overweight • According to the Centers for Disease Control and Prevention, an estimated 65% of U.S. adults aged 20 years and older are either overweight (defined as having a body mass index (BMI) of 25 or higher) or obese (defined as BMI of 30 or higher).  • Endocrinologists treat patients who are overweight or obese, sometimes because of metabolic and hormonal problems. When someone is obese they have too much body fat. Thyroid, adrenal, ovarian, and pituitary disorders can cause obesity. • Endocrinologists also identify factors linked with obesity, such as insulin resistance and genetic problems.

18. Pituitary Gland • The pituitary is often called the master gland of the body because it controls other glands. The pituitary makes several important hormones. • Over or under production of pituitary hormones can lead to infertility, menstrual disorders, growth disorders (acromegaly or short stature) and too much cortisol production (Cushing's syndrome). Endocrinologists control these conditions with medications and refer patients who need surgery. Growth • Adults with growth hormone deficiency can experience emotional distress and fatigue. Safe and effective growth hormone replacement therapy is available for people whose growth hormone is abnormal.

19. Hypertension • Hypertension is high blood pressure, and it is a risk factor for heart disease. • Up to 10% of people have hypertension because of too much aldosterone, a hormone produced in the adrenal glands. About half of these cases are caused by growths that can be removed with surgery. • Conditions such as the metabolic syndrome or a rare adrenal growth called a pheochromocytoma also may cause hypertension. These conditions also can be treated successfully.