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Flashcards in Endocrine Deck (119)
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1

MEN 1

Wermer's Syndrome

Deletion 11q12-13

3 Ps

Parathyroid hyperplasia (90%)
Pancreatic (and duodenal) islet cell tumors (50%)
Pituitary adenomas (25%) - prolactinoma = #1

2

MEN 2A

Sipple's Syndrome

RET oncogene mutation on chrom 10q11.2

Missense mutations on chrom 1

Medullary thyroid carcinoma (100%) - 20% of all medullary cancers are from MEN

Pheo (33%) - usually b/l

Parathyroid hyperplasia (50%)

3

MEN 2B

Mucosal neuroma may be earliest sign (100%) - hypertrophied lips, thickened eyelids

Medullary thyroid carcinoma (85%)
Pheo (50%)
Marfanoid habitus - skeletal abnormalities of spine (kyphosis), pectus excavatum

4

Tx for MEN syndromes

Perform subtotal or total parathyrodectomy with autotransplantation for parathyroid hyperplasia (MEN 1 and MEN 2A)

Perform total thyroidectomy for medullary thyroid cancer (MEN 2). May require nodal dissection if palpable nodes present

5

Thyroid development

Thyroid develops at base of tongue btw first pair of pharyngeal pouches, in area called foramen cecum

Thyroid gland descends down midline to its final location and develops bilobed organ with isthmus btw lobes

Remains connected to floor of pharynx via thyroglossal duct, which obliterates around month 2. May fail to go away and form a cyst or fistula instead. Usually in kids and should be removed with surg

A pyramidal lobe can be seen in 50-80% of population and represents remnant of distal thyroglossal tract. It extends superiorly from isthmus

6

Thyroid anatomical relationships

Anterior = strap muscles (sternohyoid, sternothyroid, thyrohyoid, omohyoid)

Posterior = trachea

Posterolateral = common carotids, IJ veins, vagus nerves

Parathyroid glands on posterior surface of thyroid and may be IN the capsule

7

Lymphatic drainage of thyroid

To IJ nodes

Intraglandular lymphatics connect both lobes, explaining the high frequency of multifocal tumors in thyroid

8

Vasculature of thyroid

Arteries:
1) Superior thyroid (each side)
- first branch of external carotid at level of carotid bifurc

2) Inferior thyroid (each side)
- from thyrocervical trunk of subclavian artery

3) Ima (sometimes)
- from aortic arch or innominate artery

Venous:
1) Superior thyroid vein (each side)
- drains into IJ

2) Middle thyroid vein (each side)
- Drains into IJ

3) Inferior thyroid vein (each side)
- drains to brachiocephalic vein

9

Innervation of thyroid

***1) R recurrent laryngeal nerve branches from R vagus nerve under R subclavian artery, and ascends (posterior to thyroid) to the larynx btw the trachea and esophagus

L recurrent larygneal nerve branches from L vagus, loops under aortic arch and ascends along tracheoesophageal groove to larynx.

Both innervate muscles of the true vocal cords

2) Sympathetic - superior and middle cervical sympathetic ganglia

3) Parasympathetic - from vagus nerves via branches of laryngeal nerves

10

Clinical importance of recurrent laryngeal nerve

It innervates all the intrinsic muscles of larynx except the cricothyroid (superior laryngeal nerve) and provides sensory innervation to mucous membranes below the vocal cords

It can be damaged during thyroid surgery so surgeon needs to know its course.

Damage produces ipsilateral vocal cord paralysis and results in hoarseness or sometimes SOB due to narrowed airway

11

TSH function

Causes increased formation of TH

Release of TH into circ within 30mins

Increased TH level in blood then feeds back to pit and causes decreased TSH secretion

12

Assessment and function of thyroid hormones

If T4 production goes up, both total T4 and free T4 go up

If T4 production drops, total and free T4 drop

If amount of thyroid-binding globulin changes, only the free T4 changes (not the total)

13

How much hormone do thyroid follicles store?

enough to last 2-3 months

Thus, there is no need to worry about postop hypothyroid patient who is NPO...they can resume taking their synthroid when they begin PO diet

14

Congenital anomalies of thyroid

Persistent sinus tract remnant of developing gland = thyroglossal cyst - may occur anywhere along course as a midline structure with thyroid epithelium, usually between isthmus and hyoid bone
- #1 congenital anomaly
- few symptoms but may be infected
- Easier to see when tongue is sticking out
- surgical treatment - excise the duct remnat and central part of hyoid bone (Sistrunk's operation)

Complete failure to develop

Incomplete descent = lingual thyroid or subhyoid position (if gland enlarges, patient will have earlier respiratory symptoms)
- before surgery to remove it make sure patient has other functioning thyroid tissue (70% of lingual thyroids are the only functioning thyroid)

Excessive descent = substernal thyroid

Malformation of branchial pouch

15

Causes of hyperthyroidism

1) Grave's

2) Toxic nodular goiter

3) Toxic thyroid adenoma

4) Functional metastatic thyroid cancer

5) Struma ovarii (abnormal thyroid tissue in ovary)

16

Grave's disease def

#1 cause of hyperthyroidism in USA

Autoimmune that causes excess of TH to be produced due to presence of thyroid-stimulating immunoglobulins that stimulate production of TSH

2% of american women; 6x more common in women

Onset 20-40

Families with Graves have higher risk of other AI conditions (diabetes, Addison's) and other thyroid disorders too

17

Signs of Graves

Nervousness, increased sweating, tachy, goiter, pretibial myxedema, tremor (90%)

Heat intolerance, palpitation, AFib refractory to treatment, weight loss, fatigue, dyspnea, weakness, increased appetite, exophthalmos, thyroid bruit (50-90%)

Amenorrhea, low libidio and fertility

18

Dx of Graves

TFTs - high T3 and/or T4 and low TSH (neg feedback of high hormone levels)

Radioactive iodide uptake test (RAIU) - scan shows diffusely increased uptake

19

Tx of Graves

Antithyroid drugs

Radioiodide ablation with I-131

Subtotal or total thyroidectomy

20

Choosing a Tx for Graves

1) Consider age, severity, size, surg risk, treatment side effects and comorbidities

2) Radioablation is #1 choice
- indicated for small or medium goiters if med therapy has failed, or if other options are contraindicated
- Most patients become euthyroid within 2 months
- Most ultimately require thyroid hormone replacement (Levo)
- Complications include exacerbation of thyroid storm initially
- Contraindicated in pregnancy, women of childbearing age and newborns

3) Surgery is indicated when radioablation is contraindicated or if medical management cannot be used
- Patients should be euthyroid prior to excision
- advantage over radioablation is immediate cure

4) Medical therapy
- B blockers for symptomatic relief
- Antithyroid drugs (PTU, methimazole) inhibit hormone production and peripheral conversion of T4 to T3
- KI reduces hormone production, used to shrink gland prior to surgery
- High recurrence rate with medical tx
- may cause side effects like rash, fever, peripheral neuritis
- Patients relapse if meds are D/C'd
- Check TFTs after any treatment

21

Risks of thyroid surgery

Recurrent laryngeal nerve injury

Hypoparathyroidism

Persistent hyperthyroidism (with subtotal thyroidectomy)

22

Toxic nodular goiter

"Plummer's Disease"

Causes hyperthyroidism but without the extrathyroidal symptoms

Treatment is surgical since medical therapy and radioablation has a high failure rate

Solitary nodule = lobectomy

Multinodular goiter = subtotal thyroidectomy

23

Thyroid storm (thyrotoxicosis)

Life-threatening extreme exacerbation of hyperthyroidism precipitated by surgery on an inadequately prepared patient (incomplete B blockade and noneuthyroid patient), infections, labor, iodide administration or recent radioablation

Fever, tachy, muscle stiffness, disorientation/AMS

50% with thyroid storm develop CHF

20-40% mortality

Best way to treat is by avoiding it. ppx = achieving euthyroid state preop

Tx = fluids, antithyroid meds, B-block, corticosteroids, sodium iodide or Lugol's solution (KI) and a cooling blanket

24

Causes of hypothyroidism

Autoimmune thyroiditis

Iatrogenic: s/p thyroidectomy, s/p radioablation, 2/2 antithyroid meds

Iodine deficiency

25

Signs of hypothyroidism

Infants/peds: down's like facies, failure to thrive, mental retardation ***immediate tx with thyroid hormone will minimize neuro and intellectual effects***

Adolescents/Adults: (particularly when due to AI)
- 80% female
- brady, low CO, hypotension, SOB 2/2 effusions
- fatigue, weight gain, cold intolerance, constipation, menorrhagia, low libido and fertility

Less common = yellowish skin, hair loss, tongue enlargement

26

Dx of Tx of hypothyroidism

H&P

Low T4, T3

High TSH if primary

Low TSH if secondary

Confirm with TRH challenge - TSH will not respond in secondary hypo

Thyroid autoantibodies in AI

Low Hct

ECG may show low voltage or flat/inverted T waves

Tx = thyroxine PO or IV emergently if patient presents in myxedema coma

27

Thyroiditis (Acute)

Infectious etiology = strep pyogenes, staph aureus, pneumococcus (usually via lymphatics from local infection)

Risk = female sex, goiter, thyroglossal duct

Signs = unilateral neck pain and fever, euthyroid state, dysphagia

Tx = IV ABx and surgical drainage

28

Thyroiditis ( Subacute/de Quervain's)

Post viral- URI

Risk = female

Signs = fatigue, depression, neck pain, fever, unilateral swelling of thyroid with overlying erythema, firm, and tender thyroid, transient hyperthyroidism usually preceding hypothyroid phase

Dx = made by H&P

Tx = usually self-limiting (within 6w)
= manage pain with NSAIDs

10% become permanently hypothyroid

29

Thyroiditis (Chronic/Hashimoto)

Autoimmune

Risk = down's syndrome, Turner, familial Alzheimer's, hx of radiation therapy as child

Signs = painless enlargement of thyroid, neck tightness, presence of other AI diseases

Dx = H&P + labs
- Circulating antibodies against microsomal thyroid cell, thyroid hormone, T3, T4, or TSH receptor

Path = firm, symmetrical enlargement; follicular and Hurthle cell hyperplasia; lymphocytic and plasma cell infiltrates

Tx = thyroid hormone (usually results in regression of goiter). With failure of medical tx, partial thyroidectomy is indicated

20% present with hypothyroidism at time of dx. A euthyroid state is more common

30

Riedel's Fibrosing thyroiditis

Rare

Fibrosis replaces both lobes and isthmus

Risk = other fibrosing conditions like retroperitoneal fibrosis or sclerosing cholangitis

Signs = usually remain euthyroid; neck pain, possible airway compromise; firm, nontender enlarged thyroid

Dx = often bx required to rule out carcinoma or lymphoma

Path = dense, invasive fibrosis of both lobes and isthmus. May also involve adjacent structures

Tx = with airway compromise: Isthmectomy
Without: medical treatment with steroids