Endocrine System: Hormones and Regulation

• The endocrine system consists of major endocrine glands that secrete hormones to control and regulate the activity of certain target cells or organs.

Major Endocrine Glands

• Hypothalamus
• Pituitary
• Pineal
• Parathyroids
• Thyroid
• Thymus
• Adrenals
• Pancreas (islets)
• Ovaries
• Testes
• Endocrine glands are ductless glands.
• Exocrine glands have ducts.

General Functions of Endocrine System

• Role in reproductive and central nervous system (CNS) development in the fetus
• Stimulating growth and development during childhood and adolescence
• Sexual reproduction
• Maintaining homeostasis
• Responding to emergency demands

Hormones

• Chemical substances made by endocrine glands which regulate the activity of certain target cells or organs.
• Paracrine action has a local effect.
• Endocrine organs act as endocrine glands.

Common Hormones Characteristics

• Secretion in small amounts at variable but predictable rates
• Regulation by feedback systems
• Ability to bind to specific target cell receptors

Hormone Receptor

• Hormones exert their effects by recognizing their target tissues; attaching to receptor sites in a "lock-and-key" mechanism.

Classification of Hormones

Lipid-soluble Hormones

• Steroids, thyroid hormones
• Bound to plasma proteins as they travel to target cells
• Cross the cell membrane by simple diffusion

Water-soluble Hormones

• Insulin, growth hormone, prolactin
• Circulate freely in the blood and act directly on target tissues

Hormonal Regulation

• Specific mechanisms control endocrine activity by stimulating or inhibiting hormone synthesis and secretion
• These include positive and negative feedback, nervous system control, and physiologic rhythms

Simple Feedback

Negative Feedback

• Relies on the blood level of a hormone or other chemical compound regulated by the hormone (e.g., glucose)
• The most common type of endocrine feedback system
• Results in the gland increasing or decreasing the release of a hormone
• Example: high BP and blood volume

Positive Feedback

• Increasing hormone levels cause another gland to release a hormone that then stimulates further release of the first hormone
• Something must stop the release of the first hormone or its release will continue
• Example: pregnant patient with oxytocin secretion

Nervous System Control

• Nervous system activity directly affects some endocrine glands
• Pain, fear, sexual excitement, and other stressors can stimulate the nervous system to control hormone secretion

Rhythms

• A common physiologic rhythm is the circadian rhythm
• It is a 24-hour rhythm that is driven by sleep-wake or dark-light 24-hour (diurnal) cycles
• Hormone levels and the responsiveness of target tissues fluctuate predictably during these cycles
• Example: melatonin

Endocrine Glands

Hypothalamus

• Master gland of the endocrine system
• Releases substances that either stimulate or inhibit the production and release of hormones from the pituitary gland

Releasing Hormones from the Hypothalamus, Targeting the Anterior Pituitary

• Corticotropin-releasing hormone (CRH)
• Thyrotropin-releasing hormone (TRH)
• Growth hormone-releasing hormone (GHRH)
• Gonadotropin-releasing hormone (GnRH)
• Prolactin-releasing factor (PRF)

Inhibiting Hormones

• Somatostatin (inhibits growth hormone release)
• Prolactin-inhibiting factor (PIF)

Pituitary

• Hypophysis
• Two lobes: Anterior pituitary (adenohypophysis) and posterior pituitary (neurohypophysis)
• Infundibular stalk (hypophyseal)

Anterior Pituitary (Adenohypophysis)

• 80% of the gland by weight
• Hypothalamus-hypophyseal portal system
• Hormones secreted by the anterior pituitary

Hormones Chart

• Thyroid-stimulating hormone (TSH) or thyrotropin: Target tissue is the thyroid gland. Stimulates synthesis and release of thyroid hormones and growth/function of thyroid gland
• Prolactin: Target tissue is the ovary and mammary glands in women and testes in men. Stimulates milk production in women and response to follicles plus LH/FSH in men
• Melanocyte-stimulating hormone (MSH): Target tissue is melanocytes in the skin. Melanin production in melanocytes to make skin darker
• Growth Hormone (GH) or Somatotropin: Target tissue is all body cells. Promotes protein anabolism, tissue repair and lipid mobilization and promotes catabolism
• Gonadotropic hormones: target tissue is reproductive organs, stimulate sex hormones, growth of reproductive organs and the reproductive process
• Follicle-stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Adrenocorticotropic hormone (ACTH): target tissue is adrenal cortex, fosters growth of the adrenal cortex. Stimulates corticosteroid secretion

Posterior Pituitary Gland (Neurohypophysis)

• Composed of nerve tissue and essentially an extension of the hypothalamus
• Communication between the hypothalamus and posterior pituitary occurs through nerve tracts
• Hormones secreted are antidiuretic hormone (ADH) and oxytocin, which are made in the hypothalamus

Posterior Pituitary Hormones

• Antidiuretic hormone (ADH): target tissue is renal tubules and vascular smooth muscle. Promotes reabsorption of water from the renal tubules, and vasoconstriction
• Oxytocin: target tissue is the uterus and mammary glands. Stimulates milk secretion and uterine contractility.

Pineal Gland

• Composed of photoreceptive cells
• Primary function is secretion of melatonin

Thyroid Gland

• Anterior part of the neck is in front of the trachea. Anterior to the larynx
• Consists of 2 encapsulated lateral lobes connected by a narrow isthmus
• Highly vascular
• Size is related to TSH secretion by the anterior pituitary
• Three hormones made and secreted are thyroxine (T4), triiodothyronine (T3), and calcitonin

Triiodothyronine (T3), Thyroxine (T4)

• Iodine is required for the synthesis of both T3 and T4
• Both hormones affect metabolic rate, caloric requirements, oxygen consumption carbohydrate and lipid metabolism, growth and metabolism, brain function and other nervous system activities
• TSH from the anterior pituitary gland stimulates thyroid hormone production and release
• When circulating levels of thyroid hormone are low, the hypothalamus releases hormone (TRH) which causes the anterior pituitary to release TSH
• High circulating thyroid hormone levels inhibit the secretion of both TRH from the hypothalamus and TSH from the anterior pituitary gland

Calcitonin

• Made by C cells (parafollicular cells) of the thyroid gland in response to high circulating calcium levels
• Calcitonin lowers serum calcium levels by inhibiting the transfer of calcium from the bone to blood, increasing calcium storage in bone, and increasing renal excretion of calcium and phosphorus
• Calcitonin and PTH regulate calcium balance

Parathyroid Glands

• Two pairs of parathyroid glands lie behind each thyroid lobe
• Location: on the thyroid

Parathyroid Hormone

• Hormones: parathyroid hormone/parathormone
• Major role is to regulate serum calcium levels
• Parathyroid hormone increases serum calcium levels by acting on bone, the kidneys, and indirectly on the GI tract
• Parathyroid hormone stimulates the transfer of calcium from the bone into the blood
• In the kidney, parathyroid hormone promotes calcium reabsorption and phosphate excretion
• Parathyroid hormone stimulates the renal conversion of vitamin D to its most active form which promotes calcium and phosphorus absorption in the GI tract

Relationship Between Serum Calcium, Magnesium, PTH, and Vitamin D

• When serum calcium or magnesium are low, parathyroid hormone secretion increases
• When the serum calcium or active vitamin D levels are high, parathyroid hormone secretion falls

Adrenal Glands

• Small, paired, highly vascular glands located on the upper part of each kidney
• Each gland consists of 2 parts: medulla and cortex

Adrenal Medulla

• Inner part of the adrenal gland
• Secretes the catecholamines epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine
• Essential part of the SNS's "fight or flight" response

Adrenal Cortex

• Outer part of the adrenal gland
• Secretes several steroid hormones, including glucocorticoids, mineralocorticoids, and androgens

Glucocorticoids

• Inhibit the inflammatory response and are considered anti-inflammatory Produce HCL
• Assist with stress response
• Increase blood sugar

Mineralocorticoids

• Essential for maintaining fluid and electrolyte balance
• Promotes sodium reabsorption

Sex Hormones

• Mimics the action of estrogen and progesterone

Pancreas

• Behind the stomach and anterior to the first and second lumbar vertebrae
• Has both exocrine and endocrine functions
• Hormone secreting part of the pancreas is the islets of Langerhans
• They consist of 4 types of hormone-secreting cells: α, β, delta, and F cells

Cell Types in Pancreas

• Alpha cells make and secrete the hormone glucagon
• Beta cells make and secrete insulin and amylin
• Delta cells make and secrete somatostatin
• F or PP cells secrete pancreatic polypeptide

Glucagon

• Pancreatic alpha cells release glucagon in response to low blood glucose levels, protein ingestion, and exercise
• Increases blood glucose, providing the fuel for energy by stimulating glycogenolysis, gluconeogenesis, ketogenesis
• Glucagon and insulin function in the reciprocal manner to maintain normal blood glucose levels

Insulin

• Main regulator of metabolism and storage of ingested carbohydrates, fats, and proteins
• Facilitates glucose transport into cells, transport of amino acid across muscle membranes, and the synthesis of amino acids into protein in the peripheral tissues

Diagnostic Studies

Blood Serum Tests

Urine Studies

• Glucose (urine sugar): measures amount of glucose in the urine. Assesses diabetes management
• Ketones: measures amount of ketones in the urine, assesses for diabetic ketoacidosis, a life-threatening condition seen most often in people with type 1 DM

Radiologic Studies Endocrine System

• Adrenal arteriography (angiography, adrenal): assess for arterial obstructive conditions and/or tumors of the adrenal glands
• Computed tomography: abdominal use to detect hyperplasia/tumors or pancreatic abnormalities. Brain use to detect pituitary tumor and its size and neck, can locate thyroid nodules/assess for thyroid cancer.
• Magnetic resonance Cholangiopancreatography : assess for the source of pancreatitis and used to detect pancreatobiliary tumors
• Parathyroid (parathyroid scintigraphy): scan used to find the parathyroid glands.
• Magnetic Resonance Imaging (MRI): Abdominal: Can distinguish benign tumors from adrenal cancers and brain: study of choice for radiologic evaluation of the pituitary gland and hypothalamus.
• Radioactive iodine uptake : direct measure of thyroid activity and evaluates function of thyroid nodules.
• Thyroid Scan: used evaluate to nodules of thyroid.
• Thyroid Ultrasound: evaluates thyroid nodules to determine size/characteristics

Endocrine Problems

Disorder of Anterior Pituitary Gland

Acromegaly

• Rare condition characterized by and overproduction of Growth Hormone Age: 40 to 45 years old
• Etiology: benign growth hormone secreting pituitary adenoma Pathophysiology: increase activity of anterior pituitary gland, increase production of growth hormone, increase rate of protein synthesis, increase rate of bone, muscle production Clinical manifestation: enlargement of the bony and soft tissues on the face, feet, head and enlargement of the bony and soft tissues on the face, feet, and head Diagnostic procedure: serum growth hormone levels, glucose tolerance test, MRI and CT scans
• Nursing diagnosis
  • Body image disturbance
  • Increased risk for injury
  • Ineffective Airway Clearance
  • Ineffective Coping
• Medical management
  • Surgery (Hypophysectomy) treatment of choice
  • Radiation therapy or drug therapy for tumors larger than 45 ng/mL, drug therapy consists of somatostatin analog with includes octreotide

Other Specifics of Octreotide

• Site of injection: Subcutaneous
• Frequency: 3X week

Long acting somatostatin

Site of injection: intramuscular Frequency: every 4 weeks

Gigantism

• Rare condition characterized by overproduction of growth hormone
• Pediatric acromegaly. Age: <18 y/o
• Etiology: similar with acromegaly; benign growth hormone secreting pituitary adenoma Pathophysiology: increase activity of anterior pituitary gland, increase production of growth hormone, increase rate of protein synthesis

Clinical manifestation

• Lengthened limbs
• increased muscle mass
• weak structural foundation and easy fatigability
• Increased risk of fracture Diagnostic procedure: serum growth hormone levels, glucose tolerance test, MRI,CT Scans
• Medical management
  • surgery (hypophysectomy) treatment of choice
  • Radiation therapy or drug therapy for tumors larger than 45 ng/mL, drug therapy octreotide with includes somatostatin analog

Other Specifics of Octreotide

Site of injection: Subcutaneous Frequency: 3X week

Long acting somatostatin

Site of injection: intramuscular Frequency: every 4 weeks

Hypopituitarism

• Rate disorder that involves the decrease in one or more, pituitary hormones, pan Hypo pituitaryism
• Etiology: Pituitary tumors, autoimmune disorders, pituitary infarction, destruction of pituitary gland
• Pathophysiology:
  • Decrease the activity, APG(anterior pituitary gland) hormone decrease thyroid stimulating hormone and decrease APG hormone Clinical manifestation(early)
  • headache, vision changes, loss of smell, Nausea vomiting Monitor field of vision, visual acuity, extraocular movements, and pupillary response, To decrease hormone levels and decrease fluid and or electrolyte imbalance.

Health teaching

• Avoid vigorous coughing, sneezing, and blowing the nose Other endocrine problems include Adrenal Insufficiency and Post Operative

Assessment for acromegaly and gigantism

• Assess patient with ADL
• Use of assistive devices
• Exercise and proper positioning
• Assistive devices for walking, Cane, crutches, and walkers
• Most aluminum devices have a push-button enable, their adjustment to clients height

Dwarfism

• Delay in growth potential Enema infection or allergy Decrease anterior pituitary gland Medical management artificial growth help by medication Nursing management assess body images The main 4 disorders for pituatary gland is. Acromegaly, gigiantism, dwarfism(pediatric gigaintism) , Hypo pituaitarism

Disorders of Posterior Pituitary Gland

Syndrome of Inappropriate Antidiuretic Hormone

• A.k.a arginine vasopressin and vasopressin with the Etiology of tumor, cancer, truma
• Pathophysiolgy increased body weight
• Clinical management;
  • strict I&O and daily weight
  • observe signs of hyponatremia, seizures, headache, nausea, and vomiting, decrease neurologic function

Diabetes Insipidus

• Deficient production of ADH
• Etiology: autoimmunity and radiation
• Type: Neurogenic and Nephrogenic with clinical management to maintain the normal electrolyte ranges and monitor the normal kidney function

Disorders Of Thyroid Gland

hyperthyroidism

• Hyperactivity of the thyroid gland that can causes toxicity or thryoid storm with the Etiology of graves disease
• Pathphysiology increase the activity and metabolic rates Clinical manifestation goiter and increase metabolism and hyperactivity Medical Management Medications and Nutrition Surgery if have the tumor and make sure High-calorie diet, High protein diet. Avoid high iodine foods, high fiber diet, and avoid caffeine

Post Operation Complication

• Hypoparathyroidism is a huge compication due to low calcium. and must to have a patent air aways and monitor respiration and infection Nursing Management
• Administered the medications as prescribed
• Monitor for this rythm is an administrator IV fluids and stay calm and quiet room
• And the surgery can either to remove the thyroids remove it partially or completely depending on the severity

Complications

• Goiter
• Enlarge Thyroid Gland Disorders of Parathyroid Gland-hyperparathyrodism and hypo

Explore hormone characteristics, gland types (endocrine vs. exocrine), and regulatory mechanisms. Understand hormone interactions, calcium regulation by calcitonin and PTH, and synergistic hormonal actions for calcium balance. Learn the effects of malfunctioning hormone receptors.