Presentation on theme: "Discuss the pathogenesis and imaging approach of acromegaly and gigantism Frans Naude."— Presentation transcript:
Discuss the pathogenesis and imaging approach of acromegaly and gigantism Frans Naude
Outline Definition Pathogenesis Imaging of side-effects of increased growth hormone production Imaging approach for pituitary microadenoma
Pathogenesis of acromegaly and gigantism Def :A disorder due to excessive secretion of pituitary growth hormone, characterized by progressive enlargement of the head and face, hands and feet, and thorax.
GH-secreting tumors are the second most common type of functioning pituitary adenoma. Somatotroph cell adenomas may be quite large by the time they come to clinical attention because the manifestations of excessive GH may be subtle
Gigantism If a somatotrophic adenoma appears in children before the epiphyses have closed, the elevated levels of GH (and IGF-1) result in gigantism. This is characterized by a generalized increase in body size with disproportionately long arms and legs In most instances gigantism is also accompanied by evidence of acromegaly. These changes develop for decades before being recognized, hence the opportunity for the adenomas to reach substantial size
Acromegaly increased levels of GH are present after closure of the epiphyses. growth is most conspicuous in: – skin and soft tissues; – viscera (thyroid, heart, liver, and adrenals); – bones of the face, hands, and feet. – Bone density may be increased (hyperostosis) in both the spine and the hips. – Enlargement of the jaw results in protrusion (prognathism), with broadening of the lower face – hands and feet are enlarged with broad, sausage-like fingers – Increased risk colon polyps ( increased risk for colon cancer has not been determined)
Other disturbances GH excess is also correlated with a variety of other disturbances: – gonadal dysfunction, – diabetes mellitus, – generalized muscle weakness, – arthritis, – hypertension, congestive heart failure – increased risk of gastrointestinal cancers.
Diagnosis of pituitary GH excess relies on documentation of elevated serum GH and IGF-1 levels. failure to suppress GH production in response to an oral load of glucose is one of the most sensitive tests for acromegaly.
Imaging of effects of excess GH X-ray ( skelet, soft tissue) CT U/S : organomegly (thyroid, heart, liver, and adrenals)
Skull Thickening of the cranial bones and increased density. The diplo' may be obliterated. Sella turcica, which houses the pituitary gland, may or may not be enlarged. Paranasal sinuses become enlarged Mastoid cells become over pneumatized. Prognathous jaw, one of the obvious clinical features of this condition, is apparent on the lateral view of the facial bones.
The skull shows the large sella turcica (arrow), the large frontal sinuses, and the prognathic mandible.
Hands Heads of the metacarpals are enlarged + irregular bony thickening along the margins, simulating osteophytes Increase in the size of the sesamoid at the metacarpophalangeal joint of the thumb may be helpful. Values of the sesamoid index (determined by the height and width of this ossicle measured in millimeters) greater than 30 in women and greater than 40 in men suggest acromegaly; (cant be used alone) distal phalanges; bases enlarge and the terminal tufts form spur-like projections joint spaces widen as a result of hypertrophy of articular cartilage hypertrophy of the soft tissues may also occur, leading to the development of square, spade-shaped fingers.
PA radiograph of the hands shows in a patient with acromegaly shows the wide MCP cartilage spaces. distal phalanges have a spade-like appearance.
Feet – heel pad thickness Lateral view allows an important measurement to be made: the heel-pad thickness. This index is determined by the distance from the posteroinferior surface of the os calcaneus to the nearest skin surface. Reference range: Normal 70 kg person < 22 mm. For each additional 11kg of body weight, 1 mm can be added to the basic value; 90kg person <24mm If the heel-pad thickness is greater than the established normal value, then acromegaly is a strong possibility
The lateral radiograph of the heel shows a thick fat pad.
Phenytoin (Dilantin) has been associated with calvarial thickening and enlargement of the heel pad, similar to the changes occurring in acromegaly Imaging of arthritis and metabolic bone disease,P267
Acromegaly May result in secondary OA possibly related to overgrowth of cartilage with inadequate nutrition of the thickened cartilage or its poor quality. Knees, hips, and shoulders are affected most often At first, the cartilage spaces are noted to be unusually thick – MCP cartilage space >3 mm in males >2 mm in females – hip cartilage spaces >6 mm Later cartilage space narrowing occurs as secondary arthritis develops Osteophytes may be very large Imaging of arthritis and metabolic bone disease p131
Oblique radiograph of the shoulder in patient with acromegaly shows severe cartilage space narrowing and large osteophytes. Several intra-articular bodies (arrow) are noted within the joint recesses.
Monitoring of acromegaly Biochem: GH, IGF-1 (general pituitary fx after surgery) MRI – microadenoma dx – 3–4 months after surgery :establish a baseline for future follow-up. – medical therapy should be assessed by MRI 3–6 months after starting therapy Echocariography Colonoscopy – at least 1 baseline
Imaging of microadenoma Typical pituitary MR imaging protocol includes: high-resolution imaging of the sella and parasellar regions at 3-mm thickness, before and after contrast with fat suppression. Dynamic T1-weighted imaging may be performed when a pituitary adenoma is suspected based on clinical parameters. Gadolinium contrast dose: 0,1 ml/kg High-resolution T2- weighted sequences are also usually performed.
MRI evaluation includes: assist in the identification of tumor size (2mm), invasiveness, proximity to the optic chiasm, compression of surrounding structures
CT better than MR imaging for detecting calcifications complementary to MR imaging if a primary bony lesion is suspected
Precontrast T1 images, the lesion may be slightly hypointense to the remainder of pituitary.
Gadolinium Adenomas and normal pituitary tissue have different patterns of uptake and washout following administration of intravenous contrast; due to the lower vascularity of adenomas compared with normal pituitary
Principle of enhancement Adenomas hypoenhance relative to normal tissue during the first 60 seconds following contrast administration. Thereafter, adenomas may retain contrast more than surrounding pituitary and may thus be hyperintense on delayed imaging Radiol Clin N Am 49 (2011) 549–571: imaging of the pituitary
Exception Some adenomas have direct arterial supply Some peripheral adenomas not surrounded by pseudocapsule
References Orthopedic imaging: a practical approach, Chapter 30 Imaging of arthritis and metabolic bone disease p131 Radiol Clin N Am 49 (2011) 549–571: imaging of the pituitary Musculoskeletal imaging, Klaus Bohndorf, Herwig Imhof Guidelines for Acromegaly Management: An Update.J Clin Endocrinol Metab, May 2009, 94(5):1509–1517 Current diagnosis of acromegaly. Rev Endocr Metab Disord (2008) 9:13–19