thyroid and parathyroid glands Flashcards
what makes up the thyroid and parathyroid glands?
epiglottis hyoid bone larynx superior parathyroid gland thyroid gland inferior parathyroid gland trachea
what are the lobes of the thyroid gland linked by?
isthmus of thyroid gland
what cells make up the thyroid gland??
follicles- follicle cells surrounding colloid
parafollicular cells- c cels which secrete calcitonin
what regulate thyroid hormone secretion?
thyrotropin-releasing hormone and thyroid simulating hormone
what are the thyroid hormones present in the thyroid gland?
–90% T4and 10% T3–Bound to thyroxine-binding globulin, thyroxine-binding prealbumin, or albumin
what do the thyroid hormone affect?
Affect growth and maturation of tissues, cell metabolism, heat production, and oxygen consumption
what is the role of the parathyroid gland?
–Small glands located behind the upper and lower poles of the thyroid gland–Produce parathyroid hormone
•Regulator of serum calcium
•Antagonist of calcitonin
why is calcium regulation important? what regulates it?
Calcium important in conduction of electrical impulses in nervous and muscular systems
•Calcium is the ONLY element / mineral that has its own regulatory system->the parathyroid glands
what causes regulation of calcium in the parathyroid gland?
substances that lower cAMP levels
slight decrease in serum calcium
substances that raise the cAMP levels
what does calcitonin stimulate?
calcium salt deposit in bone
calcium homeostasis of blood 9-11mg/100ml
what are the alterations of parathyroid function?
hyperparathyroidism
hypoparathyroidism
what is hyperparathyroidism?
–Primary hyperparathyroidism
•Excess secretion of PTH from one or more parathyroid glands–Secondary hyperparathyroidism
•Increase in PTH secondary to a chronic disease
what is hypoparathyroidism?
–Abnormally low PTH levels
–Usually caused by parathyroid damage inthyroid surgery
what causes hyperparathyroidism?
- Increase in the production of PTH–Usually due to a benign growth of 1:4parathyroid glands
- Induces abnormally high serum Ca++levels
- Bone decalcification
- Development of kidney stones
what are the symptoms of hyperparathyroidism?
- Fatigue
- Apathy
- Muscle weakness
- Vomiting
- Hypertension
- Demineralization of bones
- Development of kidney stones
what are the symptoms of hyperalcemic crisis?
- Acute hypercalcemic crisis can occur with calcium levels over 15 mg/dl (3.75mmol/L)
- Neurological, cardiovascular, and renal symptoms
what is the treatment aimed at decreasing serum calcium?
–IV fluids
–Phosphate therapy
–Calcitonin
–Dialysis
what causes hypoparathyroidism?
•Usually due to accidental removal of parathyroid glands during thyroid surgery
•Symptoms are due to hypocalcemia and hyperphosphatemia–Neuromuscular irritability
–Tetany
•Numbness, tingling, cramps
•Bronchospasm, laryngeal spasm, carpopedal spasm
how is the thyroid hormone synthesised?
uptake of iodine
iodination and coupling
endocytosis and secretion
how doe t4 get converted to t3?
remove an iodine
what are the 3 major thyroid-binding proteins?
- Thyroid hormone-binding globulin (TBG)–Carries approximately 70% of T4and T3
- Thyroxine-binding pre albumin (TBPA)–Binds approximately 10% of circulating T4and lesser amounts of T3
- Albumin–Binds approximately 15% of circulating T4and T
what can t4 be converted into?
t3 and rT3
what can suppress TSH secretion?
At pharmacologic doses, dopamine, somatostatin, or glucocorticoids can also suppress TSH secretion.
what is the MOA of thyroid disease?
- Dissociate of T3and T4from thyroxine-binding plasma proteins prior to entry into cells, either by diffusion or by active transport.
- In the cell, T4is enzymatically deiodinated toT3, which enters the nucleus and attaches tospecific receptors.
- The activation of these receptors promotesthe formation of RNA and subsequent protein synthesis, which is responsible for the effects of T4.
what are the major functions of thyroid hormone?
- Increases metabolism and protein synthesis
* Influences growth and development in children–Mental development and attainment of sexual maturity
what occurs in hypothyroidism?
–Decreased metabolic rate
–Accumulation of hydrophilic mucopolysaccharide substance(myxedema) in the connective tissues
–Elevated serum cholesterol
what happens in hyperthyroidism?
–Increased metabolic rate and oxygen consumption
–Increased use of metabolic fuels
–Increased sympathetic nervous system responsiveness
what are the diseases caused by hyperthroidism?
–Thyrotoxicosis–Graves disease
•Pretibial myxedema–Hyperthyroidism resulting from nodular thyroid disease
•Goiter–Thyrotoxic crisis
what is graves disease?
State of hyperthyroidism, goiter and ophthalmopathy (less commonly, dermopathy)
•An autoimmune disorder characterized by abnormal stimulation of the thyroid gland by thyroid-stimulating antibodies (thyroid-stimulating immunoglobulins [TSI]) that act through the normal TSH receptors
•Associated with human leukocyte antigen(HLA)-DR3 and HLA-B8
•Familial tendency is evident
what are the manifestations of thyroid storm?
- Very high fever
- Extreme cardiovascular effects–Tachycardia, congestive failure, and angina
- Severe CNS effects–Agitation, restlessness, and delirium
- High mortality rate
what causes primary hypothyroidism?
- Subacute thyroiditis*
- Autoimmune thyroiditis (Hashimotodisease)**
- Painless thyroiditis
- Postpartum thyroiditis
- Myxedema coma–Congenital hypothyroidism–Thyroid carcinoma
whay are the manifestations of hypothyroidism?
Mental and physical sluggishness• Myxedema •Somnolence(drowsiness or sleepiness, in excess) •Decreased cardiac output, bradycardia •Constipation •Decreased appetite •Hypoventilation •Cold intolerance •Coarse, dry skin and hair •Weight gain
what are the manifestations of hyperthyroidism?
- Thyroid storm
- 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 the difference between thyrotoxicosis and hypothyroidism in skin and appendages
T-Warm, moist skin; sweating; heat intolerance; fine, thin hair; Plummer’s nails; pretibial dermopathy(Graves’ disease)
H-Pale, cool, puffy skin; dry and brittle hair; brittle nails
what is the difference between thyro and hypo in eyes and face?
t-Retraction of upper lidwith wide stare;periorbital edema;exophthalmos; diplopia(Graves’ disease)
h-Drooping of eyelids;periorbital edema; loss oftemporal aspects ofeyebrows; puffy, nonpittingface; large tongue
what are the symptoms of exopthalmina?
- Bilateral in Graves Disease
* Unilateral in orbital tumour
what is the difference between t and h in CVS?
T-eripheral vascular resistance; ↑heart rate, stroke volume, cardiacoutput, pulse pressure;high-output heartfailure; ↑inotropic and chronotropic effects;arrhythmias; angina
h-peripheral vascular resistance; ↓heart rate, stroke volume, cardiacoutput, pulse pressure; low-output heart failure; ECG:bradycardia, prolonged PRinterval, flat T wave, lowvoltage; pericardial effusion
what is the difference between t ad g in RS?
t-Dyspnea; ↓vital capacity
H-pleural effusions; hypoventilation and CO2retention
what is the difference between t and H with GIT system?
t-of bowel movements ;hypoproteinemia
h- dec appeitite and freq of bowel movements; ascites
what is the differece between t and H in CNS?
t-Nervousness ;hyperkinesia; emotionallability
h-Lethargy; general slowing of mental processes; neuropathies
what is the difference between t and h with musculoskeletal system?
t-Weakness and muscle fatigue; increased deeptendon reflexes; hypercalcemia; osteoporosis
h-Stiffness and muscle fatigue;↓deep tendon reflexes; ↑alkaline phosphatase, LDH, AST
what are the differences n t and h with the renal system?
t-Mild polyuria; ↑renal blood flow;↑glomerular filtration rate
h-Impaired water excretion;↓renal blood flow;
what is the differnece between t and in the hematopoetic system?
t-↑erythropoiesis; anemia
h-erythropoiesis; anemia
what is the difference between t and in the reporoductive system?
t-Menstrual irregularities; increased gonadal decreased ferlitysteroid metabolism
h-Hypermenorrhea ;infertility; decreased libido; impotence; oligospermia;↓gonadal steroid metabolism
what is the difference between t and h in the metabolic system?
t-↑basal metabolic rate; negative nitrogenbalance; hyperglycemia↓cholesterol and triglycerides; ↑hormone ј requirements for fat- and water-soluble vitamins;↑drug metabolism; ↓warfarin requirement
h-↓basal metabolic rate; slight positive nitrogen balance; delayed degradation ofј ↑cholesterol and triglycerides; ↓hormone for fat- and water-soluble vitamins; ↓drug metabolism; ↑warfarin requirement
what causes hashimoto’s thyroiditis? is there a goitre?
- autoimmune destruction of thyroid
- goitre present early, absent later
- mild to severe
how is a drug induced thyroid disease caused? is there a goiter present?
blocked hormone formation
goitre present
how is dyshormono-genesis caused? is there a goitre present?
- impaired synthesis of t4 due to enzyme deficiency
goitre present
mild to severe
how is radiation , thyroidectomy caused?
destruction or removal of gland
goitre absent
severe degree of hypothyroidism
how is congenital thyroid disease caused?
athyreosis or ectipic thyroid, iodine deficiency, tsh receptor blocking antibodies
goitre absent or present
severe
how is secondary thyroid diseases caused?
due to pituitary or hypothalamic disease
goitre absent
mild
what is used to disagnose thyroid disorders?
tfts resin uptake test assessment of thyroid antibodies radioiodine uptake test thyroid scans ultrasonography CT and MRI fine-needle aspiration biopsy of a thyroid nodule
how would you asses thyroid function by lab?
sample- about 5ml o venous blood
blood plamsa- blood collected into tube containing anticoagulant
blood: collected into plain tube
request card info- drug and preexisting non-thyroid disease can affect interpretation
test also used to monitor the effectiveness of the therapy
what is the normal value for total thyroxine t4?
4-11ug/dl
what is the normal value for t3?
60-175ug/dl
what is the normal value for ft4?
0.7-1.4ng/dl
what is the normal result for ft3?
0.16-0.4ng/dl
what is the normal value for tsh?
0.4-4.5ulU/ml
what are the typical values for thyroid function tests?for subclinical primary hyperthyroidism
- Plasma /serum TSH reduced
- Plasma/serum FT4and FT3normal( often high normal)
- Greater than normal risk of developing hyperthyroidism(usually Graves disease in long term )
- Thyroid testing every 6-12 months
- Subclinical Primary hyperthyroidism increase risk of
- Atrial fibrillation in elderly
- Reduced bone density (osteoporosis) in post menopausalwomen
what are the clinical values for subclinical primary hypothyroidism?
- Serum TSH raised
- Serum FT4particularly high (>10mlU/L)
- Offered annual thyroid testing
what are the 3 treatments used in hyperthyroidism?
1- antithyroid agents
surgery
RAI
how can stress affect the hypothalamus?
decrease TRH- this decreasing levels of t3 an t4
what drugs treat hypothyroidism?
levothyroxine t4
and liothyronine t3- iv in emergency
