Metabolic and endocrine disorders



2.1: Metabolic and endocrine disorders


Harsha Chadaga


Metabolic bone diseases are a group of diseases that result in abnormalities of (a) bone mass, (b) structure mineral homeostasis (c) bone turnover or (d) growth. Endocrine disorders are a result of malfunction of endocrine systems which could be the gland, hormones, receptors or organs impacted by the hormones. These disorders can cause wide ranging effects on the body. These disorders usually arise from effects of decreased or increased secretions of the hormones. A metabolic disorder occurs when an improper level of a hormone alters the body metabolism and impacts its function.


Wilson disease is a disorder of copper metabolism which most often manifests in children and adolescents due to copper accumulation in the liver and brain resulting in hepatic dysfunction and neuropsychiatric symptom. Osteomalacia is the result of impaired mineralization of newly formed osteoid, which leads to characteristic Looser zones and bone softening. Findings of hyperparathyroidism are the result of bone resorption, most often manifesting as subperiosteal resorption in the hand followed by other parts of skeletal system. Renal osteodystrophy is a constellation of skeletal changes seen in patients with chronic renal failure and associated with changes of secondary hyperparathyroidism and can also demonstrate features of ‘rugger jersey spine’, osteomalacia and osteosclerosis. Hypoparathyroidism is most frequently due to iatrogenic injury, and on radiographs hypoparathyroidism reflects an overall increase in bone mass. Thyroid hormone is involved in regulating endochondral bone formation, and congenital hypothyroidism, if untreated, can result in delayed bone age and absent or fragmented distal femoral and proximal tibial epiphyses. Thyroid acropachy manifests as soft tissue proliferation and is most often observed in the hands and feet. Hemochromatosis refers to the accumulation of iron in the different tissues of body secondary to excess iron in the body due to multiple causes affecting the liver, spleen and skeletal system. The findings of acromegaly are due to excess growth hormone secretion and therefore result in proliferation of the bones and soft tissues.


2.1.1

WILSON’S DISEASE


Sriram Patwari



Introduction


Wilson’s disease (WD), also known as hepatolenticular degeneration, is an uncommon autosomal recessive disorder of the copper metabolism resulting from mutation of ATP7B gene. The disease was first identified by Samuel Alexander Kinnier Wilson, a British neurologist in 1912.


WD is distributed throughout the world. The reported prevalence of WD varies between 12 and 29 per 100,000 in Europeans, and prevalence of 33 and 68 per 100,000 is reported in Asian countries other than India. There are no major community-based epidemiological studies of WD in India.


Pathophysiology


The ATP7B gene is located on chromosome 13q14-21 and encodes an enzyme P-type ATPase essential for synthesis of ceruloplasmin and biliary excretion of excess copper. As a result of mutation on the ATP7B gene, there is progressive accumulation of the copper in the liver tissue, resulting in cirrhosis. The liver also releases the excess copper into the bloodstream that is unbound to ceruloplasmin, which precipitates in the brain (lentiform nucleus), eyes and kidneys (Fig. 2.1.1.1).


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Fig. 2.1.1.1 Pathophysiology of Wilson’s disease.


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Clinical presentation


WD most often manifests in children and adolescents with no specific genetic predilection. Since the most common sites of copper accumulation is the liver and brain, WD symptomatically presents with hepatic dysfunction and neuropsychiatric symptom.




  • • Hepatic dysfunction: Most common presentations are recurrent jaundice, acute hepatitis, fulminant hepatic failure, or chronic liver disease and portal hypertension. Generally, the early age of onset of the symptoms leads to a greater degree of hepatic dysfunction.
  • • Neurological symptoms: Patient’s most often present akinetic rigid state with hand tremors, masked facial expression, slurring of speech, dystonia and ataxia. “Wing beating tremor” is characteristically described in patients with Wilson’s disease. If an adolescent or young adult presents with parkinsonism-like features, Wilson’s disease should be considered in the differential diagnosis.
  • • Psychiatric symptoms: Mild cognitive deterioration and clumsiness, reduced scholastic performance, behavioural changes, depression, anxiety and psychotic disorders are known to occur in patients with WD.
  • • Other clinical features:


    1. 1. Kayser–Fleischer rings (KF rings) may be visible on the cornea either directly or through slit lamp examination and results from that position of the copper in the Descemet’s membrane. WD is also known to cause sunflower cataract. Both KF rings and sunflower cataract are pathognomonic features of WD.
    2. 2. Renal tubular acidosis, nephrocalcinosis, hypercalciuria and aminoaciduria can be seen in WD due to deposition of copper in the renal tubules.
    3. 3. WD can manifest with reduced bone mineral density, resulting in osteoporosis and insufficiency fractures. Osteomalacia, early osteoarthritis and heterotopic ossifications are also known to occur.
    4. 4. Rarely WD causes cardiomyopathy, heart failure and cardiac arrhythmias. Endocrine dysfunction including hypoparathyroidism, gigantism and infertility can be rarely seen.

Imaging


CNS manifestations


The CNS manifestations of WD is due to copper deposition in basal ganglia (especially putamen), midbrain, pons and thalamus.


CT: The role of CT is limited with widespread availability of MRI. There can be symmetrical hypodensities in bilateral basal ganglia and thalamus. In patients with long-standing WD, there can diffuse cerebral and cerebellar atrophy.


MRI





  • • Symmetrical signal changes in deep grey matter structures are seen in WD. T2 and fluid-attenuated inversion recovery (FLAIR) hyperintensity and T1 hypointensity seen in bilateral basal ganglia (predominantly involving the putamen and caudate nucleus) and lateral thalami. These changes are likely attributed to oedema/demyelination/necrosis caused by the deposition of copper. Similar signal changes are also seen in midbrain tegmentum and pons (Fig. 2.1.1.2).
  • • The involvement of the midbrain and pons in WD is manifested as classical face of giant panda (Fig. 2.1.1.3) and face of miniature panda sign.
  • • The “Face of Giant panda sign” was originally described by Hitoshi et al. in 1991 and occurs due to the T2 hyperintensity in the tegmentum with sparing of red nucleus and lateral portion of the pars reticulata of the substantia nigra and hypointensity of the superior colliculus. This sign can be seen in 12% of patients in a study done by Taly AB et al. in 2009.
  • • The “face of the miniature panda sign” has also been described in WD for the changes occurring within the pontine tegmentum. The relative T2 hypointensity of the medial longitudinal fasciculi and central tegmental tracts (forming the eyes of the panda) along with the T2 hyperintensity of the aqueduct and fourth ventricle (forming nose and mouth of the panda). The superior cerebellar peduncles resemble the panda’s cheeks.
  • • The occurrence of both face of giant panda and miniature panda sign is called as the “double panda sign”.
  • • There can be central pontine myelinolysis like changes seen in WD. Three different patterns are recognized: (1) central rounded pontine involvement with sparing of the peripheral rim, (b) bisected and (c) trisected pattern (also known as Trident/Mercedes Benz sign).
  • • Symmetric T2 hyperintensity can sometimes be seen in bilateral claustrum (Fig. 2.1.1.4), called as “bright claustrum sign”.
  • • The cases with predominant hepatic involvement show symmetrical T1 hyperintensity in bilateral globus pallidus (Fig. 2.1.1.5) and are due to hepatic dysfunction with portosystemic shunting and manganese deposition.
  • • Cerebral parenchymal involvement is not uncommon and can demonstrate diffuse asymmetrical cortical and white matter changes with predominant affection of frontal lobe.
  • • Generalized neuroparenchymal atrophy can be seen in patients with long-standing disease.

Image
Fig. 2.1.1.2 MRI in Wilson’s disease. Axial T2 weighted images showing a symmetrical hyperintensities in bilateral caudate and putamen and lateral thalami with areas of T2 hyperintensity involving the midbrain tegmentum, pons and bilateral middle cerebellar peduncles. The diffusion-weighted images show patchy areas of diffusion restriction in these areas.

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Fig. 2.1.1.3 Face of giant panda sign in Wilson’s disease. The axial T2 image at the level of midbrain in a patient with Wilson’s disease showing T2 hyperintensity in tegmentum with sparing of red nucleus and lateral portion of the past reticulata of the substantia nigra and hypointensity of the superior colliculus resembling the face of giant panda.

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Fig. 2.1.1.4 Bright claustrum sign in Wilson’s disease. Symmetrical T2 hyperintensity seen along the claustrum in a patient with Wilson’s disease.

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Fig. 2.1.1.5 Wilson’s disease with predominant hepatic involvement. Axial T1 weighted image showing symmetrical T1 hyperintensity in bilateral globus pallidus due to hepatic dysfunction with portosystemic shunting and manganese deposition.

Advanced neuroimaging





  • • Diffusion restriction can be seen early in the course of WD and is likely due to toxic effects of copper causing inflammation and some swelling.
  • • There can be a concurrent change in iron metabolism and excessive iron deposition in brain in patients with WD. This can be seen as areas of T2 hypointensity in basal ganglia and increased susceptibility on gradient echo/SWI images. Increased susceptibility can also be seen in bilateral thalami, red nucleus and substantia nigra.
  • • Role of MR spectroscopy in WD is limited. Few studies have demonstrated reduced NAA/Cr and increased mI/Cr ratio indicating neuronal damage and glial proliferation. The potential role of MR spectroscopy in assessing response to chelation therapy is also being studied.
  • • Role of diffusion tensor imaging is limited with few studies showing reduced functional anisotropy and increased mean diffusivity in normal appearing white matter suggesting a generalized and widespread involvement.

Hepatobiliary manifestations


Imaging findings include steatosis, acute hepatitis, cirrhosis and portal hypertension. In long-standing cases due to excessive copper deposition, T2 hypointense and T1 hyperintense nodules can be seen on MRI.


Musculoskeletal manifestations


Imaging findings include early osteoarthritis, chondrocalcinosis, diffuse osteopenia and secondary osteomalacia due to renal dysfunction.


Diagnosis


The important biochemical investigations in patients with WD include estimation of serum copper (reduced), serum ceruloplasmin (reduced) and 24-h urine copper (increased). The liver biopsy can be done to estimate the degree of liver parenchymal changes and quantification of copper accumulation. Genetic analysis is often performed in the mutation in ATP7b gene.


Imaging differential diagnosis





  1. a. Leigh’s disease
  2. b. Infantile bilateral striatal necrosis
  3. c. Neurodegeneration with brain iron accumulation
  4. d. Juvenile Huntington disease
  5. e. Acquired non-Wilsonian hepatocerebral degeneration
  6. f. Osmotic demyelination syndrome
  7. g. Viral encephalitis – Japanese encephalitis
  8. h. Toxic encephalopathy – methanol intoxication

Treatment and role of imaging in assessing clinical response





  • • Chelation therapy – penicillamine, trientine and zinc are most often used.
  • • Orthotopic liver transplantation is curative.
  • • MRI can be used for follow-up to assess the response to chelation therapy. There is reduction in the abnormal T2 hyperintensity after treatment which corelated with the clinical response. Few studies have also used MR spectroscopy and diffusion tensor imaging to monitor treatment response.

2.1.2

HYPERPARATHYROIDISM AND HYPOPARATHYROIDISM


Harsha C Chadaga


Hyperparathyroidism


Introduction


Hyperparathyroidism refers to increased production and secretion of parathyroid hormone from the parathyroid gland, of which there are many causes. This hormone causes increased osteoclastic activity causing widespread skeletal changes which is specific enough for radiologic diagnosis.


Pathophysiology (Fig. 2.1.2.1)


In primary hyperparathyroidism, elevated parathormone stimulates osteoclastic resorption, liberating calcium and phosphorus into the bloodstream. Phosphorus is readily excreted and owing to the constant calcium-phosphorus product, calcium is retained, disturbing homeostasis. This results in hypercalcaemia and hypophosphatemia.


Image
Fig. 2.1.2.1 Hormonal regulation of Calcium metabolism.

In secondary hyperparathyroidism, abnormal renal vitamin D formation and calcium loss creates hypocalcaemia and increases the release of parathormone and bone resorption.


The histopathologic alterations consist of osteoclastic and osteocytic resorption, with fibrous tissue replacement. The bone is decreased in density and exhibits defective lamellar structure, producing a soft, fragile bone. The pathological hallmark is subperiosteal bone resorption of the outer cortex at the insertional points of ligaments and tendons.


Clinical presentation


There are three basic forms of hyperparathyroidism: primary, secondary, and tertiary.




  • • Primary hyperparathyroidism is the most common cause of hypercalcaemia and may be sporadic or familial. This is owing to parathyroid adenoma (90% cases), hyperplasia, carcinoma or ectopic tumours producing parathormone type of substance. Characteristically elevated levels of parathormone, hypercalcaemia and hypophosphatemia is noted.
  • • Secondary hyperparathyroidism is one of the most common complications of chronic renal disease, causing persistent loss of calcium and phosphorus and thus stimulating release of parathormone.
  • • Tertiary hyperparathyroidism is seen in dialysis patients where the parathyroid gland may act independently of serum calcium levels.

Some of the syndromic associations include multiple endocrine neoplasia type I, type IIa, familial hypocalciuric hypercalcaemia and few others.


Hyperparathyroidism typically present in women 30–50 years of age with weakness, lethargy, polydipsia and polyuria. Renal calculus may be the presentation for examination sometimes. Diffuse bone pains, dementia, depression, constipation and pancreatitis are other clinical features which could be the first presentation.


Serum evaluation demonstrates



Image

Imaging

The radiological features can be discussed as


Bone resorption





  • • Subperiosteal bone resorption is most constant and specific finding. It is virtually pathognomonic of hyperparathyroidism (Fig. 2.1.2.2). This produces a lace like irregularity of cortical margin. Earliest involvement is phalangeal tufts. Typical sites of involvement are radial aspect of middle phalanx of second and third finger. The other sites of involvement include lateral end of clavicle, superior and inferior margins of ribs and lamina dura of skull and teeth.
  • • Subchondral resorption results in pseudo widening of joint space (Fig. 2.1.2.3). Some of the typical sites involved are sacroiliac joint, symphysis pubis sternoclavicular joint.
  • • Cortical resorption caused intracortical tunneling and endosteal resorption causes scalloping along inner cortical surface.
  • • Trabecular resorption causes spotty deossification with indistinct and coarse trabecular pattern resulting in granular salt and pepper skull with loss of distinction between inner and outer table (Fig. 2.1.2.4).
  • • Subligamentous/subtendinous resorption occurs at attachments of ligaments and tendons causing focal resorption of cortical bone. Frequent sites of involvement are the trochanters, humeral and ischial tuberosities, inferior aspect of distal clavicle and inferior surface of the calcaneus.

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Fig. 2.1.2.2 X-ray Both Hands AP View demonstrates diffuse osteoporosis with subperiosteal, intracortical and endosteal resorption.

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Fig. 2.1.2.3 CT pelvis demonstrates subchondral bone resorption causing widening of sacroiliac joint resorption.

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Fig. 2.1.2.4 Skull AP and Lat demonstrates multiple lytic areas in skull suggestive of “pepper pot skull.”

Bone softening: Bone softening results in basilar impression of skull, biconcave vertebral deformities with kyphoscoliosis and bowing of long bones. Bone softening also results in slipped capital femoral epiphysis.


Brown tumours: Also known as osteoclastoma, it appear as focal osteolytic areas with bone swelling. These are result of osteoclastic activity stimulated by parathormone. In the era previous to dialysis, brown tumours were more common in primary form, but now also seen in secondary. Brown tumours are typically seen in ribs, pelvic bones, metaphysis of long bones and mandible (Fig. 2.1.2.5). These are often expansile solitary lesions located eccentric or cortical with no adjacent reactive bone formation.


Image
Fig. 2.1.2.5 X-ray pelvis AP View multiple lytic areas suggestive of Brown tumours.

Osteosclerosis: More frequent in secondary hyperparathyroidism. Role of calcitonin has been implicated in osteosclerosis. This is frequently seen involving axial skeleton, pelvis and clavicle. In the spine typical “rugger jersey spine” appearance is noted secondary to osteosclerosis.


Soft tissue calcification: More frequently seen in secondary hyperparathyroidism. Typically seen around hip, knee, shoulder and wrist. Calcification of cartilage in menisci is seen and known as chondrocalcinosis (15%–18%).


Calcification is also seen in bilateral basal ganglia, dentate nuclei and subcortical white matter. Manifestations of hypercalcemia will appear as nephrocalcinosis and renal calculi. This is seen up to 75% of hyperparathyroidism patients.


Erosive arthropathy: It simulates rheumatoid arthritis with joint space preservation.


Periosteal new bone formation linear new bone formation paralleling cortical surface. This is typically seen along ileopectineal line, humerus, femur, tibia and radius.




Primary versus Secondary Hyperparathyroidism



























Radiographic Findings

Primary HyperParathyroidism

Secondary HyperParathyroidism
Osteosclerosis 0 +++
Brown Tumours +++ ++
Chondrocalcinosis ++ 0
Metastatic calcification + +++
Subperiosteal resorption + ++

+++ more common, + less common


Although US examination, CT of the neck, and magnetic resonance imaging are useful in the evaluation of primary hyperparathyroidism, 99mTc-sestamibi parathyroid scintigraphy is now the best preoperative localizing modality for the detection of parathyroid adenomas. As parathyroid scintigraphy can be sometimes limited by the coexistence of thyroid nodules or other metabolically active tissues, it is often correlated with CT results to yield functional and anatomic localization.


Differential Diagnosis: Differential for hypercalcaemia includes metastasis (second most common cause) that will have low or suppressed parathyroid hormone levels and benign familial hypocalciuric hypercalcaemia in which calcium creatinine clearance ratio is < 0.01.


Treatment: Most patients with primary hyperparathyroidism are asymptomatic, treatment is controversial. Some clinicians believe that surgical management is always appropriate given the unpredictable long-term complications including recurrent urolithiasis and osteoporosis. NIH consensus statement in 1990 concluded that surgical intervention is the acceptable treatment for primary hyperparathyroidism, surveillance is justified in patients whose calcium levels are only mildly elevated and whose renal and bone status is close to normal.


Hypoparathyroidism


Introduction


It occurs due to reduced secretion of parathyroid hormone from the parathyroid glands. Parathyroid hormone is essential in calcium metabolism and helps maintain serum calcium milieu.1 Absent or reduced parathyroid hormone results in failure to mobilize calcium from bone, reabsorb calcium from the distal nephron or activate renal 1 alpha hydroxylase activity.


Causes of hypoparathyroidism can be congenital or acquired. Some of the common congenital causes are DiGeorge syndrome, type I autoimmune polyglandular syndrome, X-linked or autosomally inherited hypoparathyroidism and PTH gene mutations.


In acquired causes there is damage to the para thyroid glands resulting in secondary hypoparathyroidism. Post-surgical hypoparathyroidism is most common acquired cause, usually following thyroid or other head and neck surgeries. Other acquired causes could be due to hemochromatosis, thalassemia major, Wilson disease or metastases (rarely).


Imaging features


Most often imaging features come into light during radiographs done for some other purpose.


Radiographs and CT


Radiography is the most commonly used modality to evaluate the skeletal and soft tissue changes of hypoparathyroidism. Osteosclerosis either localized or diffuse is most common skeletal finding seen in hypoparathyroidism. Osteosclerosis mainly involves and manifests as thickening of the facial bones and cranial vault with a widened diploe. Other findings are sutural diastasis, which is due to increased intracranial pressure.


There is calcification of ligaments mainly anterior longitudinal ligament and posterior paraspinal ligaments in the spine and muscle insertions (enthesopathy).


Hypoparathyroidism also results in hypoplastic dentition, delayed or failed eruption of the teeth, and a thickened lamina dura. Subcutaneous calcifications, mainly seen around shoulders and hips, can be seen as well. There are band-like radiodensities in the metaphysis of long bones, and sclerosis of the iliac crests and the margins of the vertebral bodies. Premature closure of the physis is also radiographic finding usually in the developing skeleton.


Intracranial calcifications mainly in basal ganglia, falx, and rarely the cerebellum and choroids plexus are seen and occurs due to the metabolic impairment. These are usually seen on CT of brain and less likely in skull radiographs (Fig. 2.1.2.6).


Image
Image
Fig. 2.1.2.6 Case of Hypoparathyroidism showing bilateral symmetrical calcifications involving dentate nucleus, basal ganglia and centrum semiovale.

Ultrasonography


Ultrasound helps in identifying renal findings seen in hypoparathyroidism. On ultrasound there is nephrocalcinosis and is usually seen in the patients receiving treatment due to the resultant calciuria.


Role of MRI: MRI is not a primary modality used to diagnose hypoparathyroidism. Findings of calcification of ligaments, osteosclerosis, intra-cranial and soft tissue calcifications are also seen on MRI performed for some other purpose and appear as hypointense signal changes in the involved tissues.


2.1.3

PSEUDOHYPOPARATHYROIDISM


Praveen Wali


It encompasses the disorders secondary to end-organ resistance to PTH, mainly kidneys and skeleton. In kidneys, the resistance is seen at the receptor levels in renal tubules and in skeletal system in the osteocytes and osteoclasts.


Renal resistance to PTH can be diagnosed by lab investigations by assessing the levels of nephrogenous cyclic AMP and urinary phosphorous levels which fail to increase after parenteral administration of PTH extract.


In skeletal system, PTH regulates calcium homeostasis. With end-organ resistance, this homeostasis is not achieved and results in hypocalcaemia. This cannot be corrected by parenteral injection of PTH extract due to end-organ resistance. Normally, PTH stimulates osteoclasts resulting in bone remodelling in normal skeleton. So the manifestations depend on whether the end-organ resistance is at the level osteoclasts or osteoblasts. If osteoclasts are resistant, then the histologic and radiologic features of osteitis fibrosa will not be observed. If the osteoclasts respond to PTH, features of increased bone remodelling with osteitis fibrosa are seen.


Based on variability in end-organ resistance, there are several clinical variants of pseudohypoparathyroidism. Subtypes are based on biochemical results and have no specific imaging findings.


Clinical variants of PHP





  • PHP I: It is associated with reduced urinary cAMP and phosphate excretion. It if further classified as follows:


    • Subtype Ia: It is autosomal dominant and is associated with resistance to PTH and other hormones that stimulate adenyl cyclase in their target tissues, such as TSH.
    • Subtype Ib: Sporadic with autosomal dominant inheritance and is associated with mainly renal resistance to PTH.
    • Subtype Ic: In this subtype, there is resistance to PTH and other hormones as well like thyroid stimulating hormone, follicular stimulating hormone and luteinizing hormone. This type of resistance is also seen in Albright hereditary osteodystrophy (AHO).

  • PHP II: In this variant, there is normal urinary cAMP excretion; however, there is decreased phosphate excretion.

Imaging manifestations


Musculoskeletal manifestations





  • • Shortening of metacarpals and metatarsals (symmetric or asymmetric) with descending order of frequency 4th, 5th, 3rd, 1st 2nd (Figs 2.1.3.1–2.1.3.4)
  • • Phalanges are short and/or deformed, usually involves distal and middle phalanges (Fig. 2.1.3.2)
  • • There can be metaphyseal resorption similar to that seen in rickets.
  • • Altered development of epiphysis in the form of premature fusion of the epiphysis and tubular bones. There can be cone-shaped epiphyses of the bones.
  • • There is trabecular widening – very nonspecific sign.
  • • There is diffuse reduction in bone density.
  • • There can be osteosclerosis due to altered parathyroid hormone milieu. There is also calvarial thickening seen.
  • • Metastatic calcification or ossification is seen in soft tissues mainly in skin, subcutaneous tissue and deep connective tissue
  • • Small bony out projections – exostoses are seen.
  • • Deformation of bones in the form of bowing of radius and ulna and bony deformities like coxa vara/coxa valga are also seen.
  • • There is abnormal dentition in the form of hypoplasia, defective dentine, widening root canals, delayed eruption of teeth, excessive caries are also seen.

Image
Fig. 2.1.3.1 Radiograph of right foot AP and oblique projections in a 25-year-old male demonstrating short fourth metatarsal.

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Fig. 2.1.3.2 Radiograph of right and left wrist and hands. AP projections in a 16-year-old male demonstrating short 4th and 5th metacarpals and deformed middle phalanges of 2nd to 5th fingers.

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Fig. 2.1.3.3 Radiograph of right foot AP and oblique projections in a 20-year-old male demonstrating short 1st metatarsal.

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Fig. 2.1.3.4 Radiograph of left hand AP projection in a 22-year-old female demonstrating short fifth metacarpal.

CNS manifestations





Image
Fig. 2.1.3.5 Noncontrast computed tomography axial section of brain in soft tissue window of a 5-year-old paediatric patient at the level of centrum semiovale demonstrating white matter calcifications on right side.

Image
Fig. 2.1.3.6 Noncontrast computed tomography axial section of brain in soft tissue window of a 5-year-old paediatric patient at the level of basal ganglia demonstrating symmetric bilateral basal ganglia calcifications.

Image
Fig. 2.1.3.7 Noncontrast computed tomography axial section of brain in soft tissue window of a 5-year-old paediatric patient at the level of posterior fossa demonstrating symmetric calcification involving bilateral dentate nuclei.

Pseudopseudohypoparathyroidism


Pseudopseudohypoparathyroidism (PPHP) is an inherited disorder and is biochemically normal but phenotypically similar to pseudohypoparathyroidism type 1a, called AHO phenotype.


These patients have similar clinical and radiological features as pseudohypoparathyroidism but without alterations in parathyroid hormone levels and calcium metabolism. There is often a family history of pseudohypoparathyroidism.


Summary


PHP and PPHP, although rare we must be aware of imaging features and must be suspected in cases with any of the above findings. Usually, majority of the findings can be imaged by radiography, whilst the CNS manifestations might need cross-sectional imaging. Imaging features in isolation are not specific and must be evaluated in entirety and along with laboratory findings.


2.1.4

HYPERTHYROIDISM AND HYPOTHYROIDISM


Harsha C Chadaga


Hyperthyroidism


Introduction


Hyperthyroidism refers to increased production and secretion of thyroid hormone from the thyroid gland. Hyperthyroidism is not synonymous with thyrotoxicosis, which refers to a clinical syndrome of excess thyroid hormone. Graves’ disease (also known as Basedow disease) is an autoimmune thyroid disease and is the most common cause of thyrotoxicosis (upto 85%).


Pathophysiology: Numerous causes of hyperthyroidism are present which include




  • • Increased thyroid gland stimulation: hCG secretion, excess TSH secretion, TSH receptor stimulating antibodies (Graves’ disease – most common cause of hyperthyroidism)
  • • Independent thyroid function: functioning adenoma, multinodular goiter
  • • Thyroid tissue inflammation: autoimmune, viral, infectious and iatrogenic
  • • Extrathyroid source: dietary and neoplastic
  • • Iodine exposure: iatrogenic

Clinical presentation: Hyperthyroidism brings a constellation of symptoms which include appetite change, insomnia, fatigue, menstrual issues, hand tremors, heart beat irregularities, bowel disturbances, weight fluctuations and many more. The combination of exophthalmos, palpitations and goiter is called the Merseburger (or Merseburg) triad.


Imaging


The radiological features can be discussed as follows:


Skeletal: Which includes diffuse osteoporosis and thyroid acropachy. Thyroid acropachy is seen in 1% of Graves’ disease. Radiographic findings of thyroid acropachy are best seen in the hands and feet, in which clubbing, periostitis and soft-tissue swelling is noted. The periostitis is greatest along the radial margins of the metacarpal, metatarsal and middle and proximal phalangeal diaphysis. Soft-tissue swelling may also be seen in the pretibial region.


CNS: Manifests as encephalopathy associated with autoimmune thyroid disease (EAATD). MRI studies are frequently normal (around 60%). When abnormalities are present they are non-specific, such T2/FLAIR subcortical white matter high signal intensities and post-contrast meningeal enhancement can be seen. Most patients respond to gluco-corticoid therapy.


Thyroid-associated orbitopathy: It is the most common cause of proptosis in adults. It is characterized by bilateral symmetrical enlargement of extraocular muscle belly giving a “coke-bottle” sign with relative sparing of tendinous insertion at globe. Involvement of the extraocular muscles in decreasing order of frequency – levator palpebrae superioris, inferior rectus, medial rectus, superior rectus, lateral rectus and oblique (Fig. 2.1.4.1).


Image
Fig. 2.1.4.1 Bilateral inferior recti, medial recti, superior recti and lateral recti muscles are hypertrophic with sparing of tendinous junctions. Minimal fatty infiltration is seen within these muscles. Source: (From author’s own collection).

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Mar 25, 2024 | Posted by in CARDIOVASCULAR IMAGING | Comments Off on Metabolic and endocrine disorders

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