Unit 6 Endocrine System Flashcards
What are the categories of endocrine function disturbance?
Hypofunction: underproduction of hormone
Causes
- Congenital defects
- Disruption in blood flow, infection, inflammation, autoimmune responses, or neoplastic growth
- Decline in function with aging
- Atrophy as the result of drug therapy or unknown reasons
- Receptor defects
Hyperfunction: excessive hormone production
Causes
- Excessive stimulation and hyperplasia of the endocrine gland
- Hormone-producing tumor of the gland
What are the categories of endocrine function disturbance?
- Primary disorders: Originate in the target gland responsible for producing the hormone
- Secondary disorders: The target gland is essentially normal, but its function is altered by defective levels of stimulating hormones or releasing factors from the pituitary system.
- Tertiary disorders
Result from hypothalamic dysfunction
Both the pituitary and target organ are under stimulated.
uncommon
What hormones are secreted by the Hypothalamus?
Seven tropic hormones are produced in the hypothalamus:
- TRH– Thyrotropin Releasing Hormone, This hormone will affect the anterior pituitary which will then affect thyroid gland activity
- PRH– Prolactin Releasing Hormone, PIH– Prolactin Release-Inhibiting Hormone, These two hormones will affect the secretion of prolactin from the anterior pituitary
- CRH– Corticotropin Releasing Hormone, This hormone affects ACTH release from the anterior pituitary
- GnRH– Gonadotropin Releasing Hormone, This hormone will affect the anterior pituitary which will then affect the gonadal release of sex hormones
- GHRH– Growth Hormone Releasing Hormone,
- SS– Somatostatin
These two hormones both affect secretion of growth hormone by the anterior pituitary
Note that all of these seven hormones are tropic hormones. Even the last one, SS, used to be called GHIH for growth hormone release-inhibiting hormone. Every single one of these hormones exerts an effect directly upon the anterior pituitary.
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What hormones are secreted by Anterior pituitary gland?
The anterior pituitary secretes four tropic hormones and two regular hormones:
- TSH– thyroid stimulating hormone, This hormone influences thyroid gland secretion of hormones.
- ACTH– adrenocorticotropic hormone, Do you see the “tropic” in its name? Good! It works on the adrenal cortex (adrenocortico-).
- LH– luteinizing hormone
- FSH– follicle stimulating hormone, These last two together are often termed “gonadotropins” because they exert a tropic hormone effect on the gonads, influencing gonadal secretion of sex hormones.
- PRL– prolactin
- GH– growth hormone
What hormones are secreted by the Posterior pituitiary gland?
Two Hormones are Produced in the Hypothalamus for Posterior Pituitary Secretion
The hypothalamus makes two additional hormones: OT (oxytocin) and ADH (antidiuretic hormone). The hypothalamus does NOT secrete these hormones, however. Instead, the neurons that make the hormones transport the hormones to their axonal terminals. These axonal terminals are located in the posterior pituitary. I edited the image from above and put it here to highlight this function. Can you imagine that one of the three neurons shown here makes OT? The other two, let's say, make ADH. After the cell bodies of these neurons make the hormones, they get transported down their axons to be released from their axonal terminals. The axonal terminals simply release the hormones into the blood, rather than onto a postsynaptic neuron. It's that easy. And this is how the hormones OT and ADH are released by the posterior pituitary into the blood. Take a look through the PowerPoint presentation and your textbook to get a feel for what these hormones do. Oxytocin is the same hormone that is injected into a woman to induce labor, but it also has some other functions. ADH may require a bit more explanation... ADH is involved in water retention in your body. ADH signals the kidneys to not allow any excess water leave the body. How does the hypothalamus know when we need to retain water? There are sensory neurons detecting visceral things, as well as sensory neurons that detect our obvious senses like touch and vision. Some visceral sensory neurons detect blood gas levels, others detect changing concentrations of fluids; the ones of this second type are called osmoreceptors (do you recognize "osmo-" from osmosis, another term about water?). If our blood starts getting to concentrated, we have to retain some more water to dilute it back out. The osmoreceptors signal the hypothalamus to secrete ADH, and our goal is accomplished.
What hormones are produced by the thyroid?
- triiodothyronine (T3) and
- thyroxine (T4),
are tyrosine-based hormones produced by the thyroid gland that are primarily responsible for regulation of metabolism.
Iodine is necessary for the production of T3 and T4. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as goitre.
The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3. The ratio of T4 to T3 released into the blood is roughly 20 to 1. T4 is converted to the active T3 (three to four times more potent than T4) within cells
What are the effects of T3 and T4?
- Increases cardiac output
- Increases heart rate
- Increases ventilation rate
- Increases basal metabolic rate
- Potentiates the effects of catecholamines (i.e. increases sympathetic activity)
- Potentiates brain development
- Thickens endometrium in females
- increase metabolism of proteins and carbohydrates
- promotes cell growth in the nervous system
How is the function of the thyroid controlled?
What are the most important function of thyroid hormone?
- Increases metabolism and protein synthesis
- Influences growth and development in children
- Mental development and attainment of sexual maturity
Describe hypothyroidism
Hypothyroidism (http://postimg.org/image/ypbp1y6f5/)
- Decreased metabolic rate
- Accumulation of hydrophilic mucopolysaccharide substance (myxedema) in the connective tissues
- Elevated serum cholesterol
Causes
- Congenital
- Lack of thyroid gland
- Anti-thyroid drugs from mother
- Acquired
- Thyroidectomy
- Goitrogenic agents
- Hashimoto thyroiditis - an autoimmune disease in which the thyroid gland is attacked by a variety of cell- and antibody-mediated immune processes
Manifestations
- Mental and physical sluggishness
- Myxedema
- Somnolence
- Decreased cardiac output, bradycardia
- Constipation
- Decreased appetite
- Hypoventilation
- Cold intolerance
- Coarse, dry skin and hair
- Weight gain
Describe hyperthyroidism.
http://postimg.org/image/ypbp1y6f5/
- Increased metabolic rate and oxygen consumption
- Increased use of metabolic fuels
- Increased sympathetic nervous system responsiveness
Causes
- Multi-nodular goitre
- Adenoma of the thyroid gland
- Grave’s disease - is an autoimmune disease. It most commonly affects the thyroid, frequently causing it to enlarge to twice its size or more (goiter), become overactive, with related hyperthyroid symptoms such as increased heartbeat, muscle weakness, disturbed sleep, and irritability. It can also affect the eyes, causing bulging eyes (exophthalmos). It affects other systems of the body, including the skin, heart, circulation and nervous system.
Manifestations
- Restlessness, irritability, anxiety
- Wakefulness
- Increased cardiac output
- Tachycardia and palpitations
- Diarrhea, increased appetite
- Dyspnea
- Heat intolerance, increased sweating
- Thin and silky skin and hair
- Weight loss
What is a thyroid storm?
Extreme, life threatening form of thyrotoxicosis
Predisposing factors:
- Manipulation of hyperactive thyroid gland
- Ketoacidosis
- Severe infection
Manifestation:
- Very high fever
- Extreme cardiovascular effects
- Tachycardia, congestive failure, and angina
- Severe CNS effects
- Agitation, restlessness, and delirium
- High mortality rate
What are the funtions of glucocorticoids (cortisol)?
- antagonistic to insulin
- protein catabolism
- lipolysis
- immune suppression
- antiinflammatory
What is the name of a disease associated with glucocorticoid excess?
Cushing’s syndrome describes the signs and symptoms associated with prolonged exposure to inappropriately high levels of the hormone cortisol. This can be caused by taking glucocorticoid drugs, or diseases that result in excess cortisol, adrenocorticotropic hormone (ACTH), or CRH levels.
Etiology
Cushing’s disease refers to a pituitary-dependent cause of Cushing’s syndrome: a tumor (adenoma) in the pituitary gland produces large amounts of ACTH, causing the adrenal glands to produce elevated levels of cortisol. It is the most common non-iatrogenic cause of Cushing’s syndrome, responsible for 70% of cases excluding glucocorticoid related cases.[2][3]
Pathophysiology
- Strictly, Cushing’s syndrome refers to excess cortisol of any etiology (as Syndrome means a group of symptoms).
- One of the causes of Cushing’s syndrome is a cortisol secreting adenoma in the cortex of the adrenal gland (primary hypercortisolism/hypercorticism).
- The adenoma causes cortisol levels in the blood to be very high, and negative feedback on the pituitary from the high cortisol levels causes ACTH levels to be very low.
- On the other hand, Cushing’s disease refers only to hypercortisolism secondary to excess production of ACTH from a corticotroph pituitary adenoma (secondary hypercortisolism/hypercorticism) or due to excess production of hypothalamus CRH (Corticotropin releasing hormone) (tertiary hypercortisolism/hypercorticism).
- This causes the blood ACTH levels to be elevated along with cortisol from the adrenal gland.
- The ACTH levels remain high because the tumor is unresponsive to negative feedback from high cortisol levels.
- Cushing’s Syndrome was also the first autoimmune disease identified in humans.[18]
Manifestations
- Extreme weight gain (truncal obesity)
- Skin striations
- Moon face
- Buffalo hump
- Immune suppression
- Water retention/edema
- Diabetes mellitus
Other
- Moodiness, irritability, or depression
- Muscle and bone weakness
- Osteoporosis
- Hypertension
- Sleep disturbances
- Menstrual disorders such as amenorrhea in women and decreased fertility in men
- Hirsutism
- Baldness
- Hypercholesterolemia
