Endocrine Flashcards
The endocrine system consists of three components
- the cell, which sends a chemical message by means of a hormone
- the target cells, or end organs, which receive the chemical message
- the environment through which the chemical is transported (blood, lymph, extracellular fluids) from the site of synthesis to the sites of cellular action.
The endocrine system controls or regulates…
metabolic processes governing energy, production, growth, fluid and electrolyte balance, response to stress and sexual reproduction.
Endocrine Glands
Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Ovaries Testes Islets of Langerhans
Structures sometimes considered endocrine glands; although they are not usually included
Pineal body
Thymus
GI glands
Placenta
Hormone
a complex chemical substance produced and secreted into body fluids by a cell or group of cells that exerts a physiologic controlling effect on other cells.
Local hormones
create their effect near the point of secretion
General hormones
produced in one organ or part of the body and are carried through the bloodstream to a distant part, or parts, of the body where they initiate or regulate physiologic activity of an organ or group of cells.
Regulation of hormonal secretion is based on:
Negative feedback.
Anterior pituitary
- Master gland
- the endocrine gland primarily responsible for stimulation and inhibition of target glandular secretions
Anterior pituitary hormones
GH –> muscles, bones, organs –> hyper = giantism –> hypo = small stature
Gonadotropin –> sex organs –> hyper = precocious puberty
ACTH –> adrenal cortex
Prolactin –> mammary; milk production –> hyper = too much milk –> hypo = no milk
TSH –> Thyroid –> hyper = overactive thyroid –> hypo = thyroid dysfunction
MSH –> skin
Posterior pituitary hormones
Oxytocin –> uterus; contractions & milk ejection –> hyper = premature ctx –> hypo = delayed/weak ctx
ADH –> kidney (distal tubules) –> hyper = SIADH –> hypo = DI
Thyroid
Thyroxine, T3, T4 –> widespread
Calcitonin –> skeleton –> stim osteoblasts –> hyper = decreased serum Ca –> hypo = weak bones
Parathyroid
PTH –> bone, kidney, GI tract –> stimulates osteoclasts –> hyper = increased serum CA, weak bones
Adrenal cortex
Glucocorticoid (wide spread), Mineral corticoids (kidney), sex hormones
Adrenal medulla
Catecholamines: 1. epinephrine, 2. norepinephrine
Pancrease
Glucagon and insulin
Gonads
Estrogen, progesterone, testosterone
Pituitary gland is controlled by:
either hormonal or neuronal signals from the hypothalamus. Hypothalamus secretes releasing hormones and inhibitory hormones.
Glandular hormones that are not under the control of the pituitary gland are:
glucagon, parathyroid hormone, antidiuretic hormone, aldosterone, and insulin
Two regulatory systems that maintain hemostasis are:
- the endocrine system
- autonomic nervous system
Collectively called neuroendocrine system
Endocrine dysfunction may result from an
intrinsic defect in the target gland (primary) or from a diminished or elevated level of tropic hormones (secondary).
An overproduction of the anterior pituitary hormones can result in:
gigantism (excess GH), hyperthyroidism hypercortisolism (Cushing syndrome), and precocious puberty (excess gonadotropins)
Panhypopituitarism
the loss of all anterior pituitary hormones, leaving only posterior pituitary function intact
**children with this condition should wear a medical bracelet.
Hypopituitarism
is defined as diminished or deficient secretion of pituitary hormones. The consequences of the condition depend on the degree of dysfunction:
Gonad. deficiency: abs./regr. of 2ndary sex charact.)
GH def: delayed somatic growth
TSH def: hypothyroidism
Corticotropin def: manifestations of adrenal hypofunction
The most common organic cause of pituitary undersecretion is
tumors in the pituitary or hypothalamic region, especially the craniopharyngiomas.
Clinical manifestations of panhypopituitarism
GH: short stature, delayed epiphyseal closure, increased insulin sensitivity
TSH: short stature, dry, coarse skin, pallor, cold intolerance, constipation
Gonad.: absence of sexual maturation
ACH: severe anorexia, weight loss, hypoglycemia, hypotension, hyponatremia, hyperkalemia, circulatory collapse
ADH: Polyuria, polydipsia, dehydration
MSH: decreased pigmentation
Familial short stature
refers to otherwise healthy children who have ancestors with adult height in the lower percentiles, and whose height during childhood is appropriate for genetic background.
Constitutional growth delay
individuals with delayed linear growth, generally beginning as a toddler, and skeletal and sexual maturation that is behind that of age-mates.
Typically these children will reach normal adult height
Clinical manifestations of hypopituitarism
children generally grow normally during the 1st year and then follow a slowed growth curve that is below the 3rd percentile; emotional problems are not uncommon, especially as they near puberty.
GH levels are increased
20 minutes after strenuous exercise and 45 to 90 minutes after the onset of sleep.
Excess GH before the closure of the epiphyseal shafts results in
proportional overgrowth of the long bones. Individuals can reach a height of 8 feet (2.4m) or more.
If oversecretion of GH occurs after epiphyseal closure, growth is in the transverse direction, producing a condition known as
acromegaly
Precocious puberty
manifestations of sexual development before age 7 for girls and age 9 for boys.
Types of precocious puberty
Central: idiopathic or congenital anomalies or infection
Peripheral: male-limited; tumors
Incomplete: premature menarche, thelarche, adrenarche
Diabetes Insipidus
The primary disorder of posterior pituitary hypofunction.
Also known as neurogenic DI, resulting from undersecretion of ADH, or vasopressin.
uncontrolled diuresis
Primary cause of DI
familial or idiopathic; of all cases, approx. 45-50% are idiopathic
Secondary causes of DI
trauma, tumors, granulomatous disease, infections, vascular anomalies
Clinical manifestations of DI
Cardinal signs: polyuria and polydipsia
1st sign if frequently enuresis
Infant: irritability relieved with feedings of water only.
Vasopressin
Tx with DI
small brown particles, which indicate drug dispersion, must be seen in the suspension
Tx is lifelong
SIADH - Syndrome of inappropriate antidiuretic hormone
Oversecretion of the posterior pituitary hormone, or ADH.
- it occurs with increased frequency in a variety of conditions: infections, tumors, CNS disease/trauma
- the most common cause of hyponatremia in the pediatric population!
SIADH manifestations
- are directly related to fluid retention and hypotonicity
- excess ADH causes most of the filtered water to be reabsorbed from the kidneys back into central circulation.
- immediate management consists of restricting fluids
Nursing considerations with SIADH
- measure I&Os
- daily weight
- monitor for s/s of fluid overload
Secretion of thyroid hormones is controlled by
TSH from the anterior pituitary.
Hyperthyroidism/hypothyroidism may result from
a defect in the target gland or from a disturbance in the secretion of TSH or TRF.
The thyroid gland is the only endocrine gland capable of
storing excess amounts of hormones for release as needed.
The main physiologic action of TH is to
regulate the basal metabolic rate and thereby control the processes of growth and tissue differentiation.
Calcitonin
helps maintain blood calcium levels by decreasing the calcium concentration.
PTH
inhibits skeletal demineralization and promotes calcium deposition in the bone.
Hypothyroidism is
one of the most common endocrine problems of childhood.