Endocrine System: Glands & Hormones

• The endocrine system promotes normal metabolism, growth, development, blood glucose control, and sexual functioning.
• The endocrine system utilizes a negative-feedback system to monitor hormone levels and adjust as needed to maintain hormone balance.

Insulin: Negative Feedback Loop

• Beta cells in the islets of Langerhans in the pancreas release insulin into the blood.
• Insulin allows body cells to become permeable to glucose.
• The liver converts glucose to glycogen.
• This process of insulin secretion lowers the increased blood glucose after a meal back to a normal level, thus maintaining homeostasis.

Glands

• Glands include the hypothalamus, pituitary, adrenal, thyroid, parathyroid, gonads, and pancreas (islet cells).
• Exocrine glands secrete via ducts outside of the body, such as lacrimation, salivation, sweat, and digestion.
• Endocrine glands secrete directly into the bloodstream and circulate to target tissues.

Hormones

• Hormones are chemical messengers that act only on target tissues to create a physiologic response.
• Hypothalamus hormones include TRH, CRH, GHRH, Dopamine, Somatostatin, and Vasopressin.
• Thyroid and parathyroid hormones include T3, T4, Calcitonin, and PTH.
• The liver produces IGF and THPO.
• The adrenal gland produces androgens, glucocorticoids, adrenaline, and noradrenaline.
• The kidney produces calcitriol, renin, and erythropoietin.
• The testes produce androgens, estradiol, and inhibin.
• The pineal gland produces melatonin.
• The pituitary gland produces GH, TSH, ACTH, FSH, MSH, LH, prolactin, oxytocin, and vasopressin.
• The thymus produces thymopoietin.
• The stomach produces gastrin, ghrelin, histamine, somatostatin, and neuropeptide Y.
• The pancreas produces insulin, glucagon, and somatostatin.
• The ovaries and placenta produce estrogen and progesterone.
• The uterus produces prolactin and relaxin.

Hypothalamus and Hypophysis (Pituitary)

• The hypothalamus creates and secretes ADH and oxytocin, then puts these hormones in the posterior pituitary for storage.
• ADH (antidiuretic hormone) increases water reabsorption in the renal tubules.
• Oxytocin stimulates uterine contractions and milk ejection (let down).
• The hypothalamus also secretes releasing and inhibiting hormones that act on the anterior pituitary to stimulate or block a response.
• The anterior pituitary (adenohypophysis) secretes TSH, ACTH, GH, FSH, LH, and prolactin.

Adrenal Glands

• The adrenal cortex produces glucocorticoids (e.g., cortisol), mineralocorticoids (e.g., aldosterone), and sex steroids (e.g., testosterone).
• The adrenal medulla produces epinephrine and norepinephrine.
• Cortisol increases blood glucose levels, breaks down proteins, builds fat, and suppresses immunity and inflammation.
• Aldosterone stimulates sodium reabsorption and potassium excretion in the kidney, regulating fluid balance.

Thyroid And Parathyroid Glands

• T3 (Triiodothyronine) and T4 (Thyroxine) plays a role in metabolism and Increase response to catecholamines.
• Thyrocalcitonin (Calcitonin) pushes calcium into bone.
• Parathyroid hormone (PTH) breaks down bone to release calcium.

Gonads

• Gonads are organs that make gametes with testes in males and ovaries in females.
• They produce haploid germ cells like spermatozoon and egg cells.
• The gonads are responsible for the maturation of reproductive organs, secondary sex characteristics, and the production of gender-specific hormones.
• FSH and LH are the hormones of the gonads.

Pancreas

• Endocrine cells are located in the pancreatic islets (islets of Langerhans).
• Alpha cells produce glucagon stimulate glycogenolysis in liver.
• Beta cells produce insulin stimulates glycogenesis in liver.
• Delta cells produce somatostatin (SS), which regulates α + β cells.

Assessment of the Endocrine System

• A chief complaint (OPQRSTU, SAMPLE) in the history, considering family history, with attention to nutrition, weight, sleep, energy, elimination, and reproductive function.
• A head-to-toe exam should focus on normal vs abnormal findings like edema, tachycardia, exophthalmos, thyroid nodules/swelling/bruit.
• Lab values include chemistry, urine, and specific hormones. It involves stimulating and suppression tests
• Imaging for pituitary and adrenal tumors is also used.

End Results of Anterior Pituitary Stimulation

• T3 and T4 affect energy and metabolism (body temperature, ATP).
• Cortisol regulates glucose and stress management.
• Aldosterone controls fluid balance and BP management.
• Epi/Norepi affects beta (heart, lungs) and alpha (vascular), specifically the pancreas.
• Growth hormone affects bone density and muscle mass.
• Progesterone, testosterone, and estrogen affect sexual maturation and reproduction.

Pituitary

• Hypopituitarism deficiencies include hypoglycemia, hypotension, hypothermia, hyponatremia, hyperkalemia, loss of bone and muscle mass, loss of menses/ovulation/reproductive abilities, hair loss, weight gain, and decreased libido.
• Hyperpituitarism excesses include hyperglycemia, hypertension, hyperthermia, hypernatremia, hypokalemia, exophthalmos, weight loss, increased bone density, coarse facial features, and irregular menses.

Transsphenoidal Hypophysectomy

• Monitor dressing drainage, swallowing, neurological status, I&O, and oral mucosa.

Risks After Pituitary Gland Removal

• Risk for hypopituitarism

Treating Hypopituitarism

• Administer TSH to stimulate the thyroid, such as levothyroxine.
• Administer ACTH to stimulate the adrenal cortex, such as mineralocorticoid (Florinef) to maintain salt/fluid (and potassium balance).
• Administer glucocorticoid (Prednisone) for glucose control.
• Administer ADH to prevent excessive water loss, such as DDAVP (Desmopressin) to promote water reabsorption.

Pediatrics and Growth Hormone

• Gigantism is excess GH prior to epiphyseal closure resultiong in proportional growth which can reach 8 feet in height.
• Acromegaly is excess GH after epiphyseal closure resulting in face/features that continue to grow. coarse in nature

Diabetes Insipidus (DI)

• Diabetes Insipidus is due to decreased ADH, resulting in polyuria.
• Specific gravity is less than 1.005, and osmolality is less than 200 mOsm/kg.
• Patients may experience polydipsia, hypernatremia, nocturia, and fluid volume deficit.
• Other symptoms are hemoconcentration, hypotension, tachycardia, thirst, skin tenting, and fatigue.
• DDAVP (Desmopressin) can be given subcutaneously, orally, or intranasally to reduce urination and restore balance.

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

• SIADH is due to too much ADH, resulting in too much water with too little urine and sodium.
• This causes dilutional hyponatremia, putting the patient at risk for seizures.
• Management includes water restriction (500-1000 ml/day), vasopressin receptor antagonists (vaptans) like conivaptan (in hospital), monitoring for signs of fluid volume overload, diuretics (with careful electrolyte monitoring) if sodium is near normal, and hypertonic saline only for very low sodium (seizure levels).

Adrenal Insufficiency (Addison Disease)

• Decreased release or efficacy of ACTH can lead to Addison's Disease.
• Patients on steroids for more than 2 weeks need to be tapered off.
• Addison's disease can develop into acute adrenal insufficiency during stress/illness.
• Treatment includes giving steroids (Solu-Cortef, Florinef).

Clinical Manifestations of Addison's Disease

• Bronze pigmentation of the skin
• Changes in distribution of body hair
• GI disturbances
• Weakness
• Weight loss
• Hypoglycemia
• Postural hypotension
• Adrenal crisis with profound fatigue, dehydration, vascular collapse, renal shutdown, decreased serum Na, and increased serum K.

Adrenal Hyperfunction (Cushing Disease)

• Hypercortisolism leads to hypertension, hyperglycemia, dependent edema with thin skin, fat maldistribution, and loss of bone density and muscle mass.
• Hyperaldosteronism leads to Conn's syndrome, fluid volume overload, hypertension, headache, hypernatremia, and hypokalemia.
• Treatment is based on the cause, including surgery (hypophysectomy, adrenalectomy), medication to suppress secretion, and medication to control symptoms.

Clinical Manifestations of Cushing's Syndrome

• Personality changes
• Moon face
• Increased susceptibility to infection
• Gynecomastia (males)
• Fat deposits on face and back of shoulders
• Osteoporosis
• Hyperglycemia
• CNS irritability
• Na and fluid retention
• Thin extremities
• GI distress
• Amenorrhea and hirsutism (females)
• Thin skin
• Purple striae
• Bruises and petechiae

Pheochromocytoma

• A pheochromocytoma is a unilateral tumor that secrets Epi/NorEpi, Alpha and Beta
• This leads to tachycardia, hypertension, headaches, palpitations, and hyperglycemia.

Adrenalectomy

• Alpha blocker needs to be administered 7-10 days prior with a goal with target is 120/80 or below, possibly beta blockade for heart rate.
• Post-op care includes monitoring vital signs and glucose as well as monitoring for Pain/bleeding/infection.

Hypothyroidism

• Decreased metabolism and energy leading to, fatigue, weight gain, and cold intolerance.
• Other symptoms of myxedema include non-pitting, puffy or waxy edema, constipation, abdominal distention, and dry skin/hair loss.
• Labs show elevated TSH, T3, T4. Treatment includes levothyroxine (Synthroid).
• Treatment is life long, levels should be checked routinely.

Pediatric Hypothyroidism

• Pediatric hypothyroidism is either infantile or juvenile onset and is damaging because the thyroid feeds the brain.
• Hallmark signs include a round abdomen, protruding umbilical hernia, a large, thrusting tongue, loss of muscle tone, and delayed development.
• It is important to treat pediatric hypothyroidism as soon as possible for best cognitive outcomes.

Myxedema Coma

• It is the most severe form of hypothyroidism.
• Symptoms include loss of diaphragmatic strength leading to hypoventilation, hypercapnia, and hypoxia.
• Other symptoms include fluid and electrolyte imbalance, hypoglycemia and hyponatremia, hypothermia, loss of cardiac function, bradycardia, and hypotension.

Hyperthyroidism/Graves Disease

• Hyperthyroidism is characterized by elevated metabolism
• Other sings include tachycardia, Thyroid bruit Heat intolerance, Increased peristalsis, Hunger/ weight loss Fatigue/nervousness/insomnia Exophthalmos Goiter
• Treatment is Anti-thyroid medication PTU Tapazole, lithium or thyroidectomy

Thyroid Storm

• Most severs hyperthyroid (thyrotoxicosis) is Thyroid Storm.
• It can lead to cardiovascular collapse
• Clinical Manifestations include Tachycardia Fever ,Hypension Abdominal pain Tremors Altered mental status
• Priorities include Airway, fluids,Beta blockers, anti-thyroid medications, steroids or Cooling blanket

Thyroid Cancer

• Radiation therapy is used for fast-growing tumors, also combination chemotherapy
• Thyroidectomy is the treatment of choice for most thyroid cancers.
• Once removed, the patient will have hypothyroidism and Hypoparathyroidism.

Thyroidectomy

• Thyroidectomy can be total or subtotal (partial).
• Patients with total thyroidectomy will be on Synthroid for life.
• Patients may also take parathyroid glands, which can lead to hypocalcemia, causing spasm of vocal cords and loss of airway.
• Post-operative concerns are airway/breathing, so have a cric/trach kit at bedside, oxygen, suction, BVM, etc.
• Circulation and watch for hemorrhage is also a consideration.

Parathyroid

• It works opposite Calcitonin.
• Hypoparathyroidism is noted by Hypocalcemia Chvostek Trousseau Tingling at mouth hands, feet.
• Treat with Administer calcium and vitamin D.
• Watch for TETANY and laryngospasm.
• Hyperparathyroidism is High Levels of Calcium Pathological fractures and Kidney stones.
• Treat with Prevent injury Fluids (dilution),Cinacalcet; a calcimimetic reduces PTH secretion and Bisphosphonates to increase BMD.