Ch 7: The Endocrine System

Endocrine System

functions to maintain homeostasis in the body with stimulation from the nervous system

Where are hormones released?

directly into the bloodstream

Hormones

chemicals that help in carrying information from one cell group to another

What is the endocrine system involved in regarding to body functioning?

growth, mood, system functions, metabolism, sexual maturity, reproduction

all are affected by illness and stress

Exocrine Glands

deliver secretions directly onto a surface

Are exocrine glands part of the endocrine system?

no

What are some examples of exocrine glands?

sweat and salivary glands

Endocrine Glands

gland type that secrete hormones directly into the bloodstream

What are some examples of endocrine glands?

hypothalamus, pituitary, pineal, thyroid, parathyroid, thymus, adrenals, reproductive glands, pancreas

Hypothalamus

controls pituitary action, major connection between nervous and endocrine systems

present in the inferior portion of the brain

Pineal

excretion of melatonin

present deep within the brain

Pituitary

secretes hormones that regulate multiple endocrine glands, called the “master gland”, has anterior and posterior lobes

located below the hypothalamus

Thyroid

secretes hormones responsible for regulating metabolism, makes thyroid-stimulating hormone (TSH), T3 and T4

present in anterior neck, butterfly-shaped

What does TSH production stimulate?

the production of triidothyronine (T3) and thyroxine (T4)

Pancreas

maintains normal blood glucose levels by secreting insulin

located in upper abdomen

Parathyroid

releases hormones (parathyroid hormone and calcitonin) to regulate blood calcium

present on dorsal aspect of thyroid

Thymus

secretes hormones involving T-cell production (stimulation and maturation)

behind the upper portion of sternum, present at birth, grows with age, and atrophies during puberty

Adrenal Glands

produce hormones that modulate stress response and regulate many body functions

on top of each kidney, triangular-shaped, outer cortex, inner medulla

Male Gonads

secrete testosterone, located in scrotum

Ovaries (Female Gonads)

secrete estrogen and profesterone

located in pelvis, produce ova (eggs)

What does the anterior pituitary produce?

growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH)

What does the posterior pituitary secrete?

oxytocin and antidiuretic hormone (ADH)

Oxytocin

helps in uterine contraction during labor, role in stimulation of flow of breast milk during breast feeding

Adrenocorticotropic Hormone (ADH)

acts on kidneys, regulates fluid and electrolyte balance

Melatonin

regulates sleep wake patterns and seasonal reactions to sunlight level alterations

What body regulation functions does the thyroid help control?

metabolic rate, bone growth, and nervous system development in children

What do the parathyroid glands promote?

calcium absorption in the gastrointestinal system and stimulate calcium re-absorption in bone

If there is high calcium content, then…

calcitonin increases

What does the adrenal cortex secrete?

corticosteroids (e.g. cortisol, aldosterone, adrenal androgens)

What does the adrenal medulla secrete?

epinephrine and adrenaline to moderate stress response

Testosterone

promote sperm production and regulates development of other secondary sexual characteristics (e.g. voice changes, growth of facial hair)

Estrogen and Progesterone

regulate breast tissue development and other secondary sexual characteristics, regulate menstruation, roles in pregnancy

Insulin and Glucagon

maintain normal blood glucose levels and reserve glucose for energy

What regulates hormone secretion?

negative feedback loops

What regulates hormone production?

nervous stimulation, endocrine control, and feedback loops

What are some examples of negative feedback loop regulation?

parathyroid stimulation occurs to release parathyroid hormone when blood calcium falls below normal

insulin secretion occurs when blood glucose elevates above normal

Hormonal Imbalance

occurs when negative feedback system unable to maintain normal hormone levels, excess or very little hormone production

What are some potential causes of diseases and disorder?

infection, injury, genetic disorder, tumor, or lifestyle

Diabetes Insipidus

results from insufficient or no production of ADH or vasopressin

ADH

secreted by posterior pituitary, anti-diuretic hormone, promotes fluid reabsorption from renal tubules

If there is little to no ADH, then…

large amounts of fluid excretion in urine, increased sodium in blood, leading to severe (often fatal) dehydration

If there is excess ADH, then…

increased permeability of renal tubules and collecting tubules in kidneys

What may cause inadequate ADH responses? What symptoms characterize these conditions?

kidney diseases and medication side effects may cause this

characterized by polyuria, polydipsia, nocturia, urine of low specific gravity, high blood plasma osmolarity

Hypopituitary Dwarfism

child has impaired height, head and trunk are of normal size, caused by insufficient or underproduction of GH from pituitary

Gigantism

hypersecretion of GH before epiphyseal plates close leading to excessive long bone growth, may reach 8 ft. tall

What are some secondary effects of a person with gigantism?

may develop diabetes mellitus

Acromegaly

oversecretion of GH in adults after the epiphyseal plates have closed; bones of the jaw, face, hands, and feet grow

What are the signs and symptoms of acromegaly? What are the complications?

signs: arthralgia, enlarged tongue, overactive sebaceous and sweat glands, coarse skin, excessive body hair, nerve damage

complications: congestive heart failure, DM, cerebrovascular abnormalities, neurologic symptoms

Hypothyroidism

reduction of thyroid hormones causing lower metabolic rate, heat loss, poor mental and physical development

What are the causes and symptoms of hypothyroidism?

causes: iodine deficiency, congenital atrophy of thyroid, infection

symptoms: fatigue, weight gain, hair loss, slower pulse, lowered body temperature, muscle cramps, menorrhagia, thick/dry/puffy skin

Simple Goiter

enlargement of any thyroid not due to infection or neoplasm

Congenital Hypothyroidism

can lead to cretinism, characterized by feeding problems, constipation, hoarse cry, sleep for extreme lengths of time

What may a newborn with congenital hypothyroidism experience?

lethargy, bradycardia, stunted skeletal growth, varying developmental delays

Myxedema

severe or chronic hypothyroidism in adults/older children

diagnosed by radioimmunoassay test for T3, T4, TSH

How are simple goiters reduced?

taking iodine, surgery, thyroid hormone replacement, medications including thyroxine doses (e.g. Levothyroid, Levoxyl, Synthroid)

hormone replacement is taken daily for life, thyroid function tests performed yearly

provider may recommend food intake that has iodine (e.g. saltwater fish, seaweed, grains)

What are the symptoms/signs of goiter in cases of hypothyroidism? How is it treated?

fatigue, weight gain, hair loss, slower pulse, lower body temperature, muscle cramps

treated with iodine supplements and thyroid hormone replacement

Hyperthyroidism

excessive thyroid hormones causing weight loss, goiter, protruding eyes (exophthalmia), tachycardia, palpitations, hypertension, agitation, nervousness, depression, tremor, excessive sweating

How is hyperthyroidism treated?

antithyroid meds (e.g. PTU, methimozole, radioactive iodine, surgical thyroidectomy), hormone replacement therapy if treatment causes hypothyroidism, orbital decompression surgery if patient has exophthalmia

What are the signs and symptoms of goiters caused by hyperthyroidism? How are they treated?

weight loss, exophthalmia, tachycardia, palpitations, etc.

treated with radioactive iodine and antithyroid medications

Addison’s Disease

adrenal gland insufficiency characterized by hypoglycemia, increased skin pigmentation, muscle weakness, fatigue, gastrointestinal disturbances

How is Addison’s disease immediately treated?

administering intravenous saline and dextrose solution and corticosteroids

Describe the potential decline in a patient with Addison’s that has deficiencies in cortisol and aldosterone

deficiencies → potassium retention, water excretion, sodium in urine → severe dehydration, low blood volume, low blood pressure, circulatory shock

What are the risks of an Addisonian crisis?

stress, surgery, infection, minor illness

manifest as life-threatening decreased blood pressure, hypoglycemia, increased blood potassium

How is Addison’s disease treated long-term?

replacing cortisol with daily glucosteroids (e.g. prednisone), replacing aldosterone with fludrocortisone (e.g. Flurinef), adding complex carbs and protein to diet, maintaining good fluid intake

How does hyperpigmentation manifest in a patient with Addison’s?

hypoglycemia, increased skin pigmentation, muscle weakness, etc. (see the pattern)

Cushing’s Syndrome

accumulation of adipose (fat) tissue in the body or trunk, symptoms of muscle wasting, hypertension, osteoporosis

What causes Cushing’s?

hyper-secretion of adrenal cortex causing increased cortisol, excessive ACTH release potentially from benign pituitary tumor

same experiences may be reported by those on corticosteroid therapy for organ transplant, severe asthma, rheumatoid arthritis

What are the symptoms of Cushing’s?

“moon face” or “buffalo hump” appearance, hyperpigmentation, wound healing problems, kidney stones, hypertension

What are some comorbidities of Cushing’s?

irritability, depression, severe psychiatric disorders, menstrual irregularities

How is Cushing’s commonly treated?

varies with the cause, usually involves cortisol controlling meds, tumor size reduction radiation therapy, tumor removal

How does hyperpigmentation present in a patient with Cushing’s?

muscle wasting, hypertension, etc. (same pattern)

Where are insulin and glucagon secreted from?

cells in the islets of Langerhans in pancreas

Diabetes Mellitus (DM)

hormonal disorder of pancreas that can occur in people of all ages and races, more common in people 60+

What are some risk factors for developing DM?

family history, certain ancestry (e.g. African Americans, Latinos, Native Americans, Asian Americans or Pacific Islanders), obesity (increased insulin resistance = increased risk), physical inactivity (reduces insulin use), autoimmune reaction (destroys islet cells, increasing type 1 risk)

What is DM characterized by?

glycosuria, polyuria, polydipsia, polyphagia, rapid weight loss, drowsiness, fatigue, itching of skin, visual disturbances, skin infections

What secondary problems commonly result from DM?

chronic hyperglycemia, carbohydrate metabolism issues

Prediabetes

no symptoms in early stages, blood tests useful for diagnoses, 15-30% of patients develop DM type 2 within 5 years without lifestyle alterations (can cause long-term vascular and cardiac damage)

DM Type 1

also called juvenile-onset diabetes or insulin-dependent. diabetes, most often in children and young adults

symptoms begin abruptly, patient becomes ill within short time period, need daily insulin injections

DM Type 2

also called adult-onset or non-insulin-dependent diabetes, slow onset of hyperglycemia, no classic symptoms so remains undetected for years

Describe the commonality and pathophysiology of DM type 2

common in 60+ African Americans, Latinos, Native Americans

Gestational Diabetes

insulin resistance at cellular level causing hyperglycemia, risk of developing DM type 2 within 5-10 years, some women show no symptoms other classes symptoms

How does gestational diabetes occur?

increased glucose in the mother’s blood crosses the placenta and enters the baby’s body

What are the complications of DM if poorly controlled?

cardiovascular disease, hypertension, ictus, renal disease, blindness, nervous system disorders, amputations, pregnancy complications, diabetic coma

Hypoglycemia

patient’s blood glucose drops below 70 mg/dL

signs/symptoms: tremors, dizziness, palpitations, diaphoresis, headache, hunger, pallor, fatigue, irritability, poor judgement, visual disturbances, convulsions, coma

Describe the four steps of treatment for a patient having a DM episode

1. glucose tablets with 5g glucose for urgent cases, if unconscious give 3 tablets (15 mg total)

2. wait 15 min. and recheck reading, if low repeat step 1

3. once symptoms relieved let patient eat normal meal

4. if symptoms persist, glucagon injection to increase blood sugar