- Consists of a group of glands that produce hormones - Works with nervous system to control and coordinate all other body systems - Effects body systems by chemical stimuli - Tissues other than endocrine glands also secrete hormones. Ie Brain, Digestive organs, kidney
- Travel through the blood to specific receptor sites. - Exert their effects on target tissue - the specificity of hormone-target cell interaction is determined by receptors in a "lock-and-key" type of mechanism. - Regulation of hormone levels in the blood depend on a highly specialized mechanism called feedback
Stimulus - change in homeostatic environment - signal sent to CNS Response - Signal sent from CNS - produce effect - Body returns to homeostasis
Positive feedback (2)
- Not common - Increases the target organ action beyond normal.
Positive feedback Classic example (6)
- action of oxytocin on uterine muscles during birth - Baby pushes on cervix sends signal to hypothalamus - Hypothalamus manufactures oxytoxin - Oxytocin is transported to posterior pituitary and released - Oxytocin stimulates uterine contraction - the loop stops when the baby leaves birth canal
Negative feedback (4)
- Most common control mechanism - like a thermostat - lack of homeostasis of a hormone in the blood or body turns on the production of said hormone at the hypothalamus and pituitary. - when homeostasis is returned, the loop is shut off.
Basic structure of a feedback loop (6)
- An environmental stimulus occurs - This stimulates the control center (aka brain-hypothalamus) - Hypothalamic hormones stimulate the pituitary - Pituitary hormones stimulate the target area - The target area produces a change - the change acts negatively or positively on the cycle.
- The "master gland" of the neuroendocrine system - Constantly monitors the body's homeostasis - analyzes input from the periphery and the CNS - coordinates response through the autonomic, endocrine, and nervous systems
- Neuronal connection to the posterior pituitary - Endocrine connection to the anterior pituitary
Hypothalamus and the anterior pituitary (4)
- The hypothalamus secretes releasing factors to cause the anterior pituitary to release stimulating hormones - These hormones act with specific endocrine glands to cause the release of hormones or stimulate cells directly - This stimulation shuts down the production of releasing factors - Leads to decreased stimulating factors and decreased hormone release.
The Hypothalamic-pituitary axis (HPA) (3)
- Most feedback loops run through this axis. - HPA mediates growth, metabolism, stress response and reproduction. - is secondarily in charge of almost everything else.
Posterior Pituitary hormones (3)
- manufactures in hypothalamus, but released from the posterior pituitary. - Oxytocin - ADH
- Target is smooth muscles of the uterus and breast. - Functions in labor and delivery, and milk ejection
- Uncommon disease that occurs in adults exposed to continuously high levels of Growth Hormone - Begins insidiously around 40-45
Acromegaly Etiology/pathophysiology (2)
- A primary GH secreting pituitary adenoma is the most common cause. - Leads to unwanted growth of bones and other soft tissue.
- occurs if high levels of growth hormone present before epiphyseal plates close
Acromegaly Clinical Manifestations (5)
- Enlargement of hands and feet - Distortion of facial features, lower jaw and forehead protrude - Enlargement of soft tissue around eyes, nose, mouth and tongue. - Skin becomes thick, leathery, oily - may have peripheral neuropathy
Syndrome of Inappropriate ADH (SIADH) (3)
- high levels of ADH without normal physiologic stimuli for release. - Released despite normal or low plasma osmolarity - Failure of negative feedback system
Syndrome of Inappropriate ADH (SIADH) Etiology/pathophysiology (2)
- Malignancy is the most common cause, especially small cell lung cancer. - can also be cause by infections, head injury, COPD, and certain drugs
Syndrome of Inappropriate ADH (SIADH) Clinical manifestations (8)
Syndrome of Inappropriate ADH (SIADH) Collaborative Care (5)
- Correct the problem - Goal is to restore normal fluid volume and osmolality - fluid restriction in Mild cases - Drugs that block ADH action on collecting tubules in more severe cases - Administration of hypertonic saline solution in cases of severe hyponatremia
- infart/necrosis of pituitary following postpartum shock or hemorrhage - Causes partial to complete loss of thyroid, adrenocortical, and gonadal function - Marked ACTH and TSH deficiency - symptoms appear hours to years post partum
Adrenal gland (3)
- The gland located atop of the kidneys - Cortex is the outer part - Inner part is the medulla
- secretes cortisol, androgens, and aldosterone (electrolytes)
Adrenal medulla (2)
- Sympathetic nervous system control - Secrete Epinephrine and Nor-epinephrine (fight or flight)
- Regulate metabolism and increase blood glucose - Critical to physiologic stress response
- Regulate sodium and potassium balance
- Contributes to growth and development in both genders. - Contributes to sexual activity in adult women
Cushing syndrome Etiology and pathophysiology (4)
- Caused by excess of corticosteroids, particularly glucocorticoids. - Most common cause is iatrogenic administration of exogenous corticosteroids. - 85% of endogenous cases due to ACTH secreting pituitary tumor - Other causes include Adrenal tumors and ectopic (abnormal) ACTH production in tumors outside the H-P-Adrenal axis (usually in the lungs or pancreas)
Cushing syndrome Etiology and pathophysiology Male vs female (2)
- Cushing disease (ACTH secreting pituitary tumor) and adrenal tumors are more common in women aged 20 - 40 - Ectopic ACTH production is more common in men
Cushing syndrome Clinical manifestations Part 1 (6)
- related to excess corticosteroids - weight gain most common feature - hyperglycemia - protein wasting - Loss of collagen - wound healing delayed
Cushing syndrome Clinical manifestations Part 2 (5)
- mood disturbances - insomnia - irrationality - psychosis - Purplish red striae on abdomen, breast or buttocks
Cushing syndrome CM: Weight Gain (4)
- Trunk (centripetal obesity) - Face ("moon face") - Cervical area (buffalo hump) - Transient weight gain from sodium and water retention.
Cushing syndrome CM: Hyperglycemia (2)
- Glucose intolerance associated with cortisol induced insulin resistance. - Increased gluconeogenesis by liver
Cushing syndrome CM: Protein wasting (3)
- Catabolic effects of cortisol - leads to weakness, especially in extremities - Protein loss in bones leads to osteoporosis, bone and back pain.
Cushing syndrome CM: Mineralocorticoid excess
- may cause hypertension secondary to fluid retention
Cushing syndrome CM: Adrenal Androgen excess (3)
May cause - pronounced acne - Virilization in women - Feminization in men
Cushing syndrome CM: Adrenal carcinomas (2)
- menstrual disorders and hirsutism in women - Gynecomastia and impotence in men.
Cushing syndrome Diagnostic studies Part 1 (4)
- 24 hour urine for free cortisol. - levels of cortisol above 80-120 mcg/day in adults indicate Cushing syndrome - Low dose dexamethasone suppression test used for borderline results of 24-hour urine cortisol - False positives can occur with depression and with certain drugs
Cushing syndrome Diagnostic studies Part 2 (4)
- Plasma cortisol levels may be elevated with loss of diurnal variation. - CT and MRI of pituitary and adrenal glands - Hypokalemia and alkalosis are seen in ectopic ACTH syndrome and adrenal carcinoma. - plasma ACTH may be low, normal or elevated depending on problem
Cushing syndrome: DS Associated findings that are not diagnostic of Cushing's (7)
- Primary goal is to normalize hormone secretion. - Drug therapy indicated when surgery is contraindicated or as adjunct to surgery - Goal of drug therapy is inhibition of adrenal function.
Cushing Syndrome Callaborative care Part 2 (4)
- Treatment depends on cause. - Pituitary Adenoma treated with surgical removal of tumor and/or radiation. - Adrenal tumors or hyperplasia is treated with adrenalectomy. - Ectopic ACTH-secreting tumors is managed by treating primary neoplasm.
Cushing Syndrome Callaborative care If Cushing's develops during use of corticosteroids (4)