Thyroid and and Parathyroid Function Flashcards
What’s a Positive Feedback Loop?
Positive Feedback Loop – increase in one action triggers increase in target
Example of a (+) Feedback Loop
Childbirth contractions trigger oxytocin, which in turn amplifies the contractions
What’s a Negative Feedback Loop?
Negative Feedback Loop – response is opposite to the perturbation
Example of a (-) Feedback Loop
Pituitary TSH and thyroid T4
What are the glands responsible for regulating the activity of the Thyroid?
Hypothalamus and pituitary regulate thyroid, as well as intrinsic regulation by the gland itself
How does Hypothalamus and Pituitary regulate Thyroid activity?
Hypothalamus produces thyroid releasing hormone (TRH), which acts on anterior pituitary
Thyroid stimulating hormone (TSH) released by anterior pituitary into blood stream
What are the 3 thyroid hormones?
Triiodothyronine (T3)
Thyroxine (T4)
Calcitonin (Weak effect on calcium-phosphorus balance)
Function of T3 and T4 (2)
T3 and T4
- regulate metabolic rate of body
- increase protein synthesis
What is Calcitonin’s function?
Weak effect on calcium-phosphorus balance
Name 2 routes that aid in Thyroid stimulation:
Vascular supply (iodine) and Sympathetic nervous system
Trace the mechanism of Thyroid stimulation (negative loop) from the Iodine in the blood stream to the TRH from the hypothalamus.
Iodine traveling in blood (from diet) absorbed into thyroid follicle cell to combine with Thyroglobulin (TGB) to form T3 and T4 (thyroid hormones)
Stimulated by TSH released by anterior pituitary into blood stream
Stimulated initially by hypothalamus TRH
What’s the best stimulus for TRH?
Exposure to cold
What’s the end result of the Thyroid negative feedback loop?
Negative feedback loop control
T3 and T4 in circulation limit production
Name 4 major actions of T3 and T4.
- Enter cell and bind with receptors in nucleus
DNA stimulated for gene expression
Altered protein synthesis within cells - Brain growth and development
- Bone growth and development
- Function of metabolism, cardiac system, heat production, glucose and fat metabolism
What are the 3 main functions of the Thyroid?
Metabolism, growth, and development
Explain how is Thyroid involved in metabolism?
Increase thermogenesis
Basal metabolic rate and heat production
Metabolic effect- Energy substrate utilization
Glucose absorption and enzyme enhancement
Lipolysis and lipolytic hormone use
Explain how is Thyroid involved in growth and development?
Growth and development
Stimulate GH release and enhanced effects
What is the cardiovascular effect of Thyroid activity?
Cardiovascular effects:
Increase HR and contractility possibly by enhancing effect of epi and norepi (release by the medulla of adrenal glands)
What are some confounding variables when trying to diagnose Thyroid dysfunction at an older age?
After age 60, thyroid may be mistaken for dementia, depression, heart disease
Name 3 risk factors for Thyroid dysfunction
family history
age (>50)
gender (female)
Name a few effects of alterations in Thyroid functioning
Alterations in thyroid can produce changes in hair, nails, skin, eyes, GI, respiratory tract, cardiovascular, neuromuscular, musculoskeletal systems – virtually everything
What test diagnoses thyroid dysfunction?
TSH (thyroid stimulating hormone) test
What is the normal range of TSH?
0.5 - 4.70 µIU/mL
Name 8 sets of characteristics specific to hypothyroidism
Fatigue, feeling run down or tired, difficulty concentrating, depression, slowed heart beats
Non tender swelling around the neck
Muscle cramps, muscle weakness
weight gain
dry, coarse itchy skin
dry, coarse thinning hair
intolerance to cold especially in the hands and feet
increased menstrual flow, irregular periods, infertility / miscarriage
constipation
Name 8 sets of characteristics specific to hyperthyroidism
Nervousness, irritability, restlessness, increased perspiration, palpitation, insomnia, heart racing, panic
Non tender swelling around the neck
Muscular weakness and tremor especially the upper arms and thighs. In later Grave’s disease eyes may bulge
weight loss
thinning skin
fine and brittle hair
intolerance to heat
less frequent periods with lighter flow
frequent bowel movements
Describe hormonal levels in hypothyroidism
High TSH, low T3, T4
Antibodies to TPO in Hashimoto’s thyroiditis
Describe hormonal levels in hyperthyroidism
Low TSH, High T3, T4
Antibodies to TSH receptors in Grave’s disease
Goiter ………..
Goiter, enlargement commonly due to lack of iodine in diet
Describe the feedback loop present in goiter in relation to dietary lack of iodine
Inhibits normal thyroid hormone production, causing hypersecretion of TSH due to lack of negative feedback loop
Almost eradicated in US due to iodized salt
clinical presentation of goiter
Would see increased neck size, pressure on trachea and esophagus, dysphagia, hoarseness, difficulty breathing
true/false “ Goiter is a hyperthyroidism condition or manifestation “
False
“goiter” term also applied to any enlargement, so can be hypo- or hyperthyroidism
What’s thyroidits?
Thyroiditis – inflammation of thyroid gland
Clinical presentation of thyroiditis
Painless thyroid enlargement, dysphagia, “tightness,” non-mechanical upper quarter pain, swollen gland, symptoms of hypothyroidism
True/false “ Thyroiditis is an exclusively endocrine disorder”
May be from infection, autoimmune disorder
some facts about Hashimoto’s thyroiditis
Hashimoto’s thyroiditis – seen more often in women in the 30-50 y.o. age group, can destroy the thyroid and result in hypothyroidism
Common name of Hyperthyroidism (thyrotoxicosis)
Graves’ disease – enlargement of the gland, protruding eyes, inflammation of ocular muscles
May first be picked up by optometrist
Three common signs of Grave’s disease:
tachycardia, fatigue, weight loss
Other s/s of Grave’s disease
hyperactive reflexes, sweating, heat intolerance, tremor, nervousness, polydipsia, dyspnea
Associated clinical presentations with Grave’s disease
Chronic periarthritis and calcific arthritis, usually in shoulder
Proximal muscle weakness, usually resolves with treatment
May see myasthenia gravis as a complication (defect in neuromuscular junction, Ach transmission)
What’s the most common Hyperthyroid Treatment?
Typically thyroidectomy
other 3 treatment for hyperthyroidism excepting thyroidectomy
+ one adjunct treatment
Antithyroid agents
Iodide
Radioactive Iodine
Beta-Adrenergic Blockers (adjunct)
what are antithyroid agents?
Antithyroid agents –drugs to inhibit thyroid hormone synthesis
How does Iodide and Radioactive Iodine work in treatment of hyperthyroidism?
Iodide-inhibit thyroid hormone biosynthesis (short term, 2 weeks)
Radioactive Iodine- selectively destroy thyroid tissue
Cancer and Graves treatment, requires monitoring of parathyroid function
How are Beta-Adrenergic Blockers used in treatment of Hyperthyroidism?
Beta-Adrenergic Blockers for symptom suppression (tachycardia, restlessness, palpitations) - adjunct to primary treatment
What brings on a thyroid storm?
Usually seen in undiagnosed thyroid disease, or precipitated by trauma, surgery, infection
Clinical presentation of a thyroid storm:
Hypermetabolism, with severe tachycardia, heart failure, shock, hyperthermia (105° F)
Do you do PT with a patient immediately after a thyroid Storm?
NO
True/False
Hypothyroidism is more common than hyperthyroidism
True
General presentation of Hypothyroidism
Insufficient hormone production, generalized depression of metabolism
If present in fetal development, usually results in cretinism - congenital birth defect
Name the 2 types of Hypothyroidism and briefly describe the mechanism
Primary – reduced function of thyroid tissue or impaired hormonal synthesis
Secondary (less common) – impaired due to pituitary dysfunction
Hypothyroidism- rate of occurrence (age, sex)
Women 10X more likely than men, increasing with age
Name one other cause of hypothyroidism ( not primarily hormonal)
May also be caused by medications (lithium, amiodarone)
One obvious clinical presentation of Hypothyroidism
Ichthyosis – dry, scaly skin
more in table 11-5
S/S of Myxedema (form of Hypothyroidism)
connective tissue changes due to increased mucopolysaccharides and proteins, causing a boggy, pitting edema in eyes, hands, feet, supraclavicular area;
thickening of tongue and oropharyngeal complex, with slurred speech
Dense, viscous synovial fluid – “bulge sign” at knee
Calcium crystals, chondrocalcinosis
Clinical presentation of Myxedema / associated conditions:
Flexor tenosynovitis, CTS
Pain and proximal muscle weakness
May have a prolonged DTR due to slow muscle contraction
TrPs, diffuse aches and cramps
Medical and therapeutic interventions for Myxedema
Proper treatment of thyroid and soft tissue work, strengthening
True/ False
Thyroid Neoplasm is relatively rare and slow-growing
True
Thyroid Neoplasm Prevalence
Caucasian females over 40
S/S of Thyroid Neoplasm
Asymptomatic nodules in thyroid, hoarseness, hemoptysis, dyspnea, elevated BP
Two type of treatments for Hypothyroidism
Increase iodine intake
Thyroid hormone replacement- Synthroid or other drugs to mimic T3 or T4 or both
Parathyroid Function:
Calcium homeostasis
Short description of PTH activity and calcium secretion:
What type of feedback?
PTH released when there is a reduction in blood calcium levels- negative feedback loop
Stimulates calcium production in bone, kidney and GI tract
Effect of PTH at high levels over bones, kidney and GI:
Bone- High PTH levels increases osteoclasts (breakdown bone)
Kidney- High PTH increases reabsorption of Ca++ while eliminating phosphate
GI- PTH and vitamin D metabolism stimulating calcium absorption from intestines
What’s the normal balanced state of bone formation?
What;s determined by?
Bone function- balance between bone formation (osteoblasts) and mineral resorption (osteoclasts)
Body framework
Calcium pool
Effect of increased secretion of PTH over bone:
Prolonged and continuous release of Parathyroid Hormone
Accelerates bone breakdown
Effect of normal secretion of PTH over bone:
Normal intermittent PTH
Enhance bone formation
Role of Vitamin D in Bone Mineral Homeostasis
Consumed in diet or produced from UV light in skin
Role is to enhance bone formation by increasing calcium and phosphate minerals necessary;
limits PTH release, thereby limiting catabolism
Role of Calcitonin in Bone Mineral Homeostasis
Calcitonin- thyroid hormone
Physiologic antagonist of PTH
Stimulates bone formation and therefore lowers Ca++ in blood
Also enhances phosphate incorporation into bone formation
Role of different Glucocorticoids in Bone Mineral Homeostasis
Glucocorticoids (steroids discussed previously)- catabolic effect on bone
Prostaglandins- stimulate bone resorption
Estrogen, androgens, GH, insulin, and thyroid hormones enhance bone formation
Presentation of Hyperparathyroidism
Hyper- postmenopausal women Excessive PTH Excessive bone demineralization Excessive calcium in blood Decreased bone density Kidney stones
Presentation of Hypoparathyroidism
Hypo- injury or accidental removal or autoimmune Hypocalcemia Hypophosphatemia Neuromuscular irritability Cardiac irritability
Necessary daily intake of calcium and Vitamin D (supplements)
Hyper and hypocalcemia
Calcium supplements, ~ 1000 units/day
Vitamin D ~ 2000 units/day
What is the role of Calcitonin?
Calcitonin- decreases blood Ca++
Treat hypercalcemia
Other mineral involved in osteoporosis and Paget’s disease:
Biophosphonates- osteoporosis, Paget’s disease, others
Fosamax, Aredia, etc.
Why is estrogen therapy used in postmenopausal women?
Estrogen therapy for post menopausal women and ovariectomy (also called oophorectomy) to preserve bone density
Short presentation of Osteoporosis
Age related bone remodeling and body type
Breakdown is greater than build-up
Bone growth and storage into the 20’s - diet and exercise puts bone in the bank!
Systemic and bilateral
Fracture and deformity risk systemically
Short Clinical Presentation of Paget’s:
Larger bone but weaker - Fracture risk, deformity
Specific area not systemic - Pelvis, spine, skull, tibia (unilateral), etc.
True/False
Paget’s is a genetic or viral infection
True
Treatment for parathyroid dysfunctions (7)
Exercise - Stretching, strengthening, balance Assistive device/bracing Sunlight Surgery Diet/Supplements Smoking- quit Alcohol consumption- moderation
