Thyroid Flashcards
1
Q
Normal Thyroid
- Weight
- Gross look
- Histo
A
- 20-25 g
- right lobe, isthmus, left lobe
- follicle lined by cuboidal to low columnar follicular cells; contain parafollicular or “C” cells which secrete calcitonin
2
Q
Hypothalamus-Pituitary-Thyroid Axis
- Hypo releases
- Pituitary releases
- Thyroid releases
- Inhibition
- Actions of T3/T4
A
- TRH onto pituitary
- TSH onto Thyroid
- T4
- Feedback inhibition by T3/T4 on Pituitary and Hypothalamus
- stimulation of protein synthesis; upregulation of carb and lipid metabolism; increase basal metabolic rate; critical role in the development of brain in fetuses and neonates
3
Q
Thyrotoxicosis
- Define
- Most common cause
A
- hyper metabolic state due to increased circulating levels of thyroid hormones
- hyper functioning of the thyroid gland
4
Q
Thyrotoxicosis Disorders
- Associated w/ Hyperthyroidism: Primary
- Associated w/ Hyperthyroidism: Secondary
- Not associated w/ Hyperthyroidism
A
- Diffuse toxic hyperplasia (Grave’s Disease), Hyperfunctioning (toxic) multinodular goiter, Hyperfunctioning (toxic) adenoma, iodine induced hyperthyroidism, neonatal thyrotoxicosis associated w/ maternal Grave’s disease
- TSH secreting pituitary adenoma
- Granulomatous (deQuarvain) thyroiditis (painful); subacute lymphocytic thyroiditis (painless); struma ovarii (ovarian teratoma w/ ectopic thyroid); factitious thyrotoxicosis (exogenous thyroid intake)
5
Q
Hyperthyroidism/Thyrotoxicosis: Clinical Manifestations (10)
11. Due to what?
A
- Increased BMR- soft, warm, flushed skin
- heat intolerance and excess sweating
- characteristic weight loss despite increased apetite
- CV- increased CO, tachycardia, palpitations, cardiomegaly, arrhythmias (uncommon) especially atrial fibrillation; development of low output heart failure;
- Neuromuscular: nervousness, emotional lability, insomnia, muscular weakness, fine tremor of hands
- Proximal muscle weakness and decreased muscle mass
- GI: hypermotility, malabsorption and diarrhea
- Ocular: wide staring gaze, lid lag
- Thyroid opthalmopathy (exophthalmos)
- Bone resorption w/ osteoporosis
- excess of thyroid hormones and over activity of sympathetic nervous system
6
Q
Hyperthyroidism: Dx
- What 3 things are measured?
- Describe TRH stimulation test
- Describe Radioactive Iodine Uptake test
- What does diffuse uptake indicate?
- Localized uptake?
- reduced uptake?
A
- TSH (usually decreased); T4 (usually increased); T3 (rare pts w/ nl or reduced T4 but elevated T3)
- injection of TRH; normal rise in TSH exclude pituitary associated hyperthyroidism
- used after dx of thyrotoxicosis
- Graves
- toxic adenoma
- thyroiditis
7
Q
Hypothyroidism
- Define
- Primary Causes (7)
- Secondary Causes (2)
A
- hypermetabolic state secondary to inadequate levels of thyroid hormones
- Developmental, Thyroid hormone resistance syndrome, post ablative, autoimmune hypothyroidism, iodine deficiency, drugs, congenital biosynthetic defect
- Pituitary Failure, Hypothalamic failure
8
Q
Hypothyroidism
- Most common cause of what physical symptom?
- Worldwide congenital hypothyroidism most often due to what?
- Most common cause where (2) isn’t a problem?
- Other clinical manifestations (2)
A
- enlargement of the gland (goiter)
- endemic iodine deficiency in diet
- chronic autoimmue thyroiditis (Hashimoto’s)
- cretinism and myxedema
9
Q
Cretinism
- Define
- Cause
- What determines the severity?
- Symptoms
A
- hypothyroidism in infants or early childhood
- secondary to iodine deficiency (endemic) or rarely from inborn errors in metabolism
- timing of the deficiency; if maternal thyroid deficiency occurs before fetus develops thyroid that develops own T3/T4, will be more severe
- Impaired development of skeletal muscles and CNS
10
Q
Myxedema
- Define
- Symptoms (6)
- What does it do to blood lipids?
A
- adult hypothyroidism
- gradual slowing of mental and physical activity
- fatigue, lethargy, apathy, slowed speech
- cold intolerance, reduced sweating
- overweight, constipation
- periorbital edema, thick coarse skin, enlarged tongue; (deposition of glycosaminoglycans)
- Reduced cardiac output causes shortness of breath and decreased exercise capacity
- promotes atherogenic profile (increased total cholesterol and LDL) –> adverse CV mortality rates
11
Q
Hypothyroidism: Lab findings
- T4
- TSH
- What is seen in primary hypothyroidism?
- Secondary?
A
- decreased
- most sensitive test for hypothyroidism
- increased TSH (thyroid not making enough T4)
- decreased/normal TSH (suggest pit tumor, necrosis; not enough TSH being produced)
12
Q
Thyroiditis
- Define
- Causes with pain (2)
- causes w/o or w/ little pain
A
- inflammation of thyroid gland
- infectious thyroiditis, subacute granulomatous thyroiditis (De Quervain thyroiditis- most common cause of painful thyroiditis)
- Subacute lymphocytic thyroiditis; Reide’s thyroiditis; Hashimoto’s thyroiditis
13
Q
Hashimoto Thyroiditis
- Define
- What areas get it?
- What age group is it found in?
- Is there a genetic component?
- 3 Mechanisms
A
- autoimmune destruction of the thyroid gland: hypothyroidism
- areas without iodine deficiency
- 45-65
- yes
- T cell-mediated cytotoxicity; Activated macrophages causing thyrocyte injury, Antibody-dependent cell-mediated immunity
14
Q
In general, which gender gets thyroid disorders/neoplasms more often?
A
Women
15
Q
Hashimoto Thyroiditis
- Labs show antibodies to what? (3)
- Gross look
- Histo look
A
- Thyroglobulin and Thyroid peroxidase (TPO-most common); TSH receptor, Iodine receptor
- diffusely enlarged gland with intact capsule; well demarcated from adjacent structures; cut surface is pale, yellow tan, somewhat nodular and firm
- parenchyma infiltrated by mononuclear inflammatory cells; Hurthle cells/oncocytes line Thyroid follicles and have abundant granular pink cytoplasm
16
Q
Hashimoto Thyroiditis: Clinical Course
- What happens physically?
- How quickly does hypothyroidism develop?
- what do some pts develop?
- Increased risk of developing what diseases (3)
A
- painless enlargement of gland w/ some degree of hypothyroidism
- gradually
- transient hyperthyroidism (due to disruption of follicles and release of T3/T4); gradually hypothyroidism sets in
- Increased risk of other autoimmune disease
- Increased risk of developing Non Hodgkin B cell lymphoma
- May have increased risk of developing papillary carcinomas
17
Q
Subacute/Granulomatous (De Quervain) Thyroiditis
- Etiology
- Clinical Course?
- Histo look:early
- Histo look: late
- Gross look
A
- Viral or post-viral inflammatory response: viral Ag or virus-induced host tissue damage stimulates formation of cytotoxic T cells which then damage the thyroid follicular cells
- self-limited; pt is asymptomatic after acute stage
- disruption of follicles w/ collections of neutrophils forming microabscesses
- aggregates of lymphocytes. plasma cells, and activated macrophages around damaged thyroid follicles;
- uni/bilateral, enlarged and firm w/ intact capsule
18
Q
Granulomatous (De Quervain) Thyroiditis
- Commonly Causes what
- Does the thyroid enlarge?
- What is commonly in pt’s history?
- How long does hyperthyroidism last?
- What is elevated in hyperthyroidism phase?
- How long does it last?
A
- thyroid pain
- variable
- upper respiratory infection
- 2-6 weeks
- elevated T3 and T4; diminished TSH, radioactive iodine uptake is diminished
- 6 to 8 weeks
19
Q
Subacute Lymphocytic Thyroiditis
- What causes pt to come in?
- Who gets it?
- Etiology
- Clinical Course
- Gross look
- Histo look
A
- mild hyperthyroidism, goitrous enlargement of thyroid, or both
- middle aged women; can also occur in post-partum period
- variants of hashimoto
- majority of pts are euthyroid by 1 year, 1/3 progress to overt hypothyroidism over 10 yrs
- mild enlargement
- lymphocytic infiltration w/ germinal centers; no fibrosis or hurthle cell metaplasia
20
Q
Riedel Thyroiditis
- Etiology
- Histo look
- Gross look
- May be associated with what?
A
- unknown
- extensive fibrosis involving the thyroid and contiguous neck structures
- hard and fixed mass, simulating cancer
- idiopathic fibrosis at other sites like retroperitoneum