Endocrine HARC Lectures Flashcards
Where is the thyroid gland located?
• Lies anterior and just below the thyroid cartilage
Isthmus overlies which tracheal rings
2-4
Thyroid secretes which three hormones
Secretes 3 key hormones: • Thyroxine (T4) • Tri-iodothyronine (T3) • Calcitonin
Thyroid development
- Thyroid development begins at _ weeks
- As an invagination of _______ in pharynx floor
- Grows as “_____ _________”
- Diverticulum descends into neck and forms thyroid gland
- Lengthening of epithelia connects thyroid to pharyngeal floor
- “Thyroglossal duct”
- Thyroglossal duct regresses, severing connection between ______ and ________
- Thyroid development begins at 4 weeks
- As an invagination of endoderm in pharynx floor
- Grows as “thyroid diverticulum”
- Diverticulum descends into neck and forms thyroid gland
- Lengthening of epithelia connects thyroid to pharyngeal floor
- “Thyroglossal duct”
- Thyroglossal duct regresses, severing connection between pharynx and thyroid
What are thyrohlossal cysts?
How can you tell a patient has it
In adults, remnant of thyroid diverticulum can be seen as foramen caecum
• Ask patient to protrude their tongue • Thyroglossal cysts will elevate
Function of patent thyroglossal duct
- Patent thyroglossal duct allows secretion of mucus which accumulates
- Infection leads to thyroglossal cyst
- Accounts 79% of neck lumps
- Full excision of track/fistula
What is a pyramidal thyroid lobe?
Extends superiorly from isthmus of the thyroid gland
- Fibrous tissue connecting pyramidal lobe with hyoid bone may contain levator thyroid muscle
- Aband of connective tissue, often containing thyroid tissue may continue from pyramidal lobe to hyoid bone
- ~50% of thyroid glands have a pyramidal lobe
What is parathyroid ectopia
By definition, ectopic parathyroid glands are parathyroid glands that are not located in the standard position in the body
Funciton of parathyroid gland
- Usually located close to upper and lower poles of each thyroid lobe [see far right image]
- Secrete parathyroid hormone (PTH)
- PTH involved in calcium homeostasis, esp. in hypocalcaemia
- Stimulates osteoclastic activity, Ca2+ dietary absorption and renal reabsorption
Explain pituitary development?
- Pituitary gland consists of 2 parts – ant. & post.
- Anterior connects to hypothalamus only through portal vessels (“adenohypohphysis”)
- Posterior is direct extension of hypothalamus (“neurohypophysis”)
- Both derived from neuroectoderm of embryo but different parts
- Anterior pituitary derived from pharynx (rathke’s pouch)
- Posterior pituitary derived from floor of diencephalon
Pituitary Development
Pituitary Development
Pituitary Development
WHat is pituitary hypoplasia?
Pituitary Hypoplasia, also known as hypoplasia of the pituitary gland, is related to congenital hypopituitarism and isolated growth hormone deficiency, type ii
Characterised by short stature, slow growth
- Failure of development of rathke’s pouch
- No GH, TSH, ACTH, FSH, LH but post. pituitary okay
- May result from deficiency of GHRH
What is congenital dysgenesis?
atypical formation
What is 46 XX dysgenesis
- No oestrogen produced. No inhibition of FSH/LH at pituitary
- Delayed or no puberty, affects physical characteristics and likely causes infertility
What is 46 XY dysgenesis
- Testis development depends on testis determining factor in SRY region of Y chromosome
- Lack of testosterone or anti-mullerian hormone production
- Failure of Wolffian ducts and development of genitalia. Female* external genitalia may also be present
Dysgenesis may relate to other karyotypes like?
Trisomy X, 47 XXY, 48 XXXY, 49 XXXXY
What are the 5 steps for neck examination?
- Inspection 2. Palpation 3. Percussion 4. Auscultation 5. Special tests
What are the blue and red sections called?
- Anterior triangle Red
- Posterior triangle Blue
What is a scintigraphy?
- 2D Nuclear medicine scan
- Radioactive isotope of iodine given
- Normal uptake 15-25%
- High uptake – Graves’ Disease
- Low uptake – Thyroiditis
- Uneven uptake – nodule
- Can be used at distant sites to assess for metastases
What is TC 99m Sestamibi and SPECT
Tc 99m Sestamibi
- Test for hyperparathyroidism/adenoma
- Sestamibi localises in mitochondria in PT glands
- Absorbs faster in hyperfunctioning PT (eg adenoma)
- Image at 2hrs when thyroid is cleared
SPECT (single positron emission CT)
- 3D imaging with higher resolution
- In addition to Tc 99m sestamibi for superior detection of adenomas in carotid sheath or mediastinum
- Normal CT limited use in thyroid imaging – useful to assess for metastases
WHat is MRCP
MRCP (Magnetic Resonance CholangioPancreatography)
- Non-invasive imaging technique with no radiation exposure
- Allows imaging of intra- and extra-hepatic biliary tree & pancreatic duct system
- Diagnostic range equivalent to the ERCP
- ERCP = “endoscopic retrograde cholangiopancreatography”
- Can replace ERCP in high risk patients to avoid significant risk of morbidity
What is Funfuscopy?
(aka ophthalmoscopy) • Examination of internal structures of eye and fundus • With an ophthalmoscope!
What does the fundus consist of?
Retina • Optic disc • Macula • Fovea • Posterior pole
WHat are the 3 layers posterior to lens?
- Sclera (outer)
- Choroid (middle)
- Retina (inner)
What are the two layers of the retina?
Neural (inner) layer
Pigmented (outer) layer
What does the neural layer of the retina consists of/function?
- Visual part consists of photoreceptive cells in posterior & lateral portion of eye
- Rods – low light photosensitivity and generally peripheral
- Cones – colour vision and high acuity
- Only attached around optic nerve & ora serrata • Susceptibility to ‘detached retina’
What does the pigmented outer layer of the retina do?
- Absorbs light not captured by photoreceptors; prevents internal reflection
- Amitotic and accumulates granules with age
- fundus appears darker in young people
What is the blood supply to the retina?
The retina is supplied by the central retinal artery and the short posterior ciliary arteries (Fig 2.3). The central retinal artery travels in or beside the optic nerve as it pierces the sclera then branches to supply the layers of the inner retina (i.e., the layers closest to the vitreous compartment).
What are you looking for when doing a funduscopy?
- Arteriolar narrowing – hypertensive retinopathy?
- Hard exudate – waxy yellow blotches
- Cotton wool spots – infarcts of neural layer (severe retinopathy)
- Neovascularisation – net of small curly vessels = proliferative retinopathy
What is the optic disc
- Represents formation of optic nerve
- Blind spot – no photoreceptive cells
- Retinal vessels trace toward optic disc
What are the 3 Cs when doing a funduscopy?
- Contour - Blurred edges – papillodoema; raised ICP?
- Colour - Orangey-pink (well perfused) with pale centre (cup)
- Cup-to-disc ratio (approx. 0.3) - If > may indicate reduced health retina. Glaucoma?
What is the macula?
- Oval area of intense pigmentation temporal to optic disc
- Fewer blood vessels here preserves visual acuity
- Contains fovea at centre
What is the fovea?
- High concn of photoreceptive cells
- Area for high visual acuity
- Macular degeneration – loss of central vision
What is the posterior pole?
Area of the retina between optic disc and macula
What is Retinal Photography
- High quality digital colour image of fundus
- More accurate than traditional funduscopy
- Allows comparison between visits to monitor condition
- Essential component of diabetic eye screening
What is Diabetic Retinopathy?
Diabetic retinopathy is a complication of diabetes, caused by high blood sugar levels damaging the back of the eye (retina). It can cause blindness if left undiagnosed and untreated. However, it usually takes several years for diabetic retinopathy to reach a stage where it could threaten your sight.
Diabetic Retinopathy leads to?
- Leading cause of blindness in working age people
- Poor glycaemic control damages small retinal vessels
- Ischaemia and infarct of retinal tissue
- Eventually leads to arterial proliferation
- Increased risk of retinal detachment
What is grading like for diabetic retinopathy?
Stage 1 = Background Retinopathy • Non-proliferative • Microaneurysms
Stage 2 = Pre-proliferative Retinopathy • Moderate non-proliferative retinopathy • Many intra-retinal haemorrhages • Venous beading ≥2 quadrants
Stage 3 = Proliferative Retinopathy • New vessels; vitreous haemorrhage
Diabetic maculopathy • Exudate +/- haemorrhage within macula
What is diabetic Neuropathy?
Diabetic neuropathy is a type of nerve damage that can occur if you have diabetes. High blood sugar (glucose) can injure nerves throughout your body. Diabetic neuropathy most often damages nerves in your legs and feet.
Affects fo Diabetic Neuropathy?
Neuronal damage due to microvascular damage
- Occlusion of vasa nervorum
- Nerve becomes ischaemic
Hyperglycaemia affects Schwann cells
- Reduced conduction velocity; later demyelination
Lost & altered sensation in early neuropathy
- Later impaired proprioception; unrecognised injury
- Atrophy of intrinsic foot musculature but not long flexors causes high arches, toe-clawing, pressure redistribution & callus formation on sole
Motor Invervation
Thigh: Posterior
Anterior
Medial
Leg: Posterior
Anterior
Medial
Thigh
- Anterior – femoral n.
- Posterior – sciatic n.
- Medial – obturator n.
Leg
- Posterior – tibial n. (& foot)
- Anterior – deep fibular n.
- Posterior – superficial fibular n.
Sensory Innervation
What is diabetic foot?
People with diabetes are prone to foot problems that develop due to prolonged periods of high blood sugar levels. Diabetic neuropathy and peripheral vascular disease are the two main foot problems that occur, and both can have serious complications.
• Macro- & microvascular dysfunction in chronic diabetes • Atherosclerosis, endothelial cell changes • Results in neuropathy, ulceration, infection • Impaired wound healing – gangrene, amputation
What is Osteomyelitis?
- Loss of protective sensation
- Wound may fester for weeks, invading bone
What is Charcot’s arthropathy?
- Altered foot mechanics – repeated (undetected) fractures
- Destroys normal foot architecture
How to prevent diabetic foot?
Vigilant maintenance of foot hygiene is best prevention
Osteomyelitis
Risks
Patho
Treatment
Risks
- Diabetes, splenectomy, trauma, IV drug use
Pathogenesis
- Infection invades bone from foot ulcer
- Most commonly ‘tripod’ bones:
- 1 st & 5th metatarsal and calcaneus
Treatment
- Antibiotics and surgical debridement
- Chronic condition problematic in diabetes due to poor O2 and wound healing
- Amputations if severe
What do you see in Xrays MRI, CT with osteomyelitis
X-ray
- 1 st line but not sensitive in early OM (<2 wks)
- Regional osteopenia, periosteal reaction, focal bony lysis or cortical loss, loss of trabecular architecture, peripheral sclerosis
MRI (best diagnostic)
- Marrow changes, oedema, cortical thickening, bone abscess, periosteal reaction
- Contrast agent to outline abscess cavities
CT
- Only if patient has contraindication for MR
Patho of Charcot’s Arthropathy
• Pathogenesis
Peripheral neuropathy – lost coordination & sensation
Gait favours mechanical stress and causes injury
Pro-inflammatory response encourages osteoclastogenesisis, consequent osteolysis
Chronic, progressive degeneration
What is usually affected first with Charcot’s Arthropathy
- Tarso-metatarsal joints commonly affected first
- Bony structures fragmented & damaged
- Coalesce into new architecture, affects arches
- Extreme conditions can lead to ‘ro
What is Bone Densitometry
Assessment of bone mineral density (BMD)
- Bone volume as proportion of tissue volume
- Classified by standard deviations (SD) from a reference population
- Important diagnostic test for osteoporosis
What is DEXA?
A DEXA scan is a quick and painless procedure that involves lying on your back on an X-ray table so an area of your body can be scanned.
• DEXA is gold standard diagnostic • Dual-energy x-ray absorptiometry • Accuracy at hip >90% • Gives T-score and Z-score • T-score: value related to peak bone mass. >2.5 SD away from mean = osteoporosis • Z-score: value related to age-matched normal. Used to measure progress of osteoporosis
