CLINICAL CORRELATIONS

Hypothyroidism or other causes of low calcium levels

What can the Trousseau's sign indicate?

Carpopedal spasm

What is the response in a positive Trousseau's sign?

Hypoparathyroidism

A physical examination finding of carpopedal spasm induced by a blood pressure cuff inflated above systolic pressure for 3 minutes is suggestive of what condition?

Hypocalcemia

What condition is Chvostek's sign used to help diagnose?

Contraction of facial muscles upon tapping the facial nerve

What is a positive Chvostek's sign?

Hyperparathyroid patients

What type of patients might need drugs that target the calcium-sensing receptor (CaSR)?

Decreased extracellular fluid calcium ion concentration inhibits these pathways and stimulates PTH secretion

How does low calcium affect PTH secretion via CaSR?

Increased extracellular fluid calcium ion concentration stimulates these pathways and decreases PTH secretion

How does high calcium affect PTH secretion via CaSR?

Sudden removal of parathyroid hormone

What is a common scenario that can lead to a rapid decrease in calcium levels?

6-7 mg/dL

To what range can calcium levels fall in 2-3 days after sudden parathyroid hormone removal?

Hypoparathyroidism

A decrease in osteocytic resorption of exchangeable calcium and inactive osteoclasts leads to a decrease in calcium release, characteristic of what condition?

Hypercalcemia, prolonged repolarization (QT interval prolongation)

What electrocardiogram finding can be observed in hypercalcemia?

Hyporeflexia

What might be the result when using a reflex hammer on a person with hypercalcemia?

Shortened QT interval, constipation

What are some clinical manifestations of hypercalcemia?

Prolonged QT Interval

In an ECG reading, what can be observed when a person has hypocalcemia?

Hypocalcemia

Carpopedal spasm and respiratory arrest are potential outcomes of what electrolyte imbalance?

Hypercalcemia

Constipation is more commonly associated with hyper- or hypocalcemia?

Transient hypoparathyroidism or decreased PTH

What might be the initial consequence of a thyroidectomy that results in the removal of three parathyroid glands?

Hypertrophy and consequently produce sufficient PTH

How might the remaining parathyroid tissue compensate after partial removal?

Hypoparathyroidism

Carpopedal spasm and obstructed respiration can be signs of what condition related to calcium regulation?

Decreased estrogen

In a postmenopausal patient, what hormonal change could confirm increased osteoclast activity?

Chronic renal disease

What is a common cause of insufficient calcitriol production leading to secondary hyperparathyroidism?

Decreased calcium reabsorption in the intestines

How does insufficient calcitriol production affect calcium levels?

Insulinoma

In very hypoglycemic patients, what pancreatic tumor is a consideration?

Endogenous production

The presence of C-peptide indicates that insulin is from what source?

Exogenous (pharmaceutical)

The absence of C-peptide indicates that insulin is likely from what source?

Measure endogenous function through radioimmunoassay

Why is C-peptide clinically significant even though it has no insulin activity?

Insulin concentration is hard to determine because it is the difference between how much has been secreted and cleared, with most clearance happening in the portal circulation

Why is it difficult to measure endogenous insulin concentration directly?

Hypoglycemia

In what clinical scenario can measuring C-peptide help determine the source of excessive insulin?

Sulfonylureas

What class of drugs increases insulin release by stimulating the ATP-sensitive potassium channel in beta cells?

Diazoxide, Phenytoin, Vinblastine, Colchicine

Name some drugs that inhibit insulin release.

Glucose concentration > 70 mg/dL (3.9 mmol/L)

At what blood glucose level does insulin synthesis get stimulated?

Hyperglycemic state

What state are brain cells protected from by GLUT3's high affinity for glucose?

Hypoglycemic state

What state might brain cells enter if they did not have GLUT3 transporters with high glucose affinity?

Diabetes

What condition is associated with disorders of insulin secretion or action?

Hyperglycemia

What is the consequence of the body's decreased ability to store extra glucose in liver glycogen in diabetic conditions?

Glycosuria

What occurs when plasma glucose levels exceed the renal threshold for reabsorption in diabetes?

Polyuria, polydipsia

What are the osmotic consequences of glucosuria in uncontrolled diabetes?

Increased lipolysis and ketone body formation

What metabolic shifts occur due to decreased glucose utilization in insulin deficiency, potentially leading to diabetic ketoacidosis?

Diabetic ketoacidosis

What serious condition can result from excessive ketone body production in uncontrolled diabetes?

Primary hyperthyroidism

What is indicated by low TSH and high thyroid hormones?

Graves’

What condition can be tested for using TSH Receptor Antibodies (TRAb)?

Radioactive Iodine (RAI) uptake and scan

What imaging technique can be used to further evaluate hyperthyroidism?

Primary hypothyroidism

What is indicated by high TSH and low free T4 and T3?

Hashimoto thyroiditis

What is the most common cause of primary hypothyroidism in iodine-sufficient areas?

Increased sweating, weight loss, heat intolerance

Name three common symptoms of hyperthyroidism.

Constipation

Is constipation more commonly associated with hyper- or hypothyroidism?

Growth retardation

What is the effect of hypothyroidism on growth?

Excessive skeletal growth

What is the effect of hyperthyroidism on growth?

Anxiety, paranoia

What are some excitatory effects of hyperthyroidism on the CNS?

Weak muscles (due to protein catabolism)

What is the effect of hyperthyroidism on muscle strength?

Sluggish muscles, relax slowly after contraction

What is the effect of hypothyroidism on muscle function?

Increased reactivity of neuronal synapses in spinal cord

What causes muscle tremor in hyperthyroidism?

Constant tiredness, difficulty to sleep

What are some effects of hyperthyroidism on sleep?

Somnolence

What is the effect of hypothyroidism on sleep?

Cretinism

What condition results from hypothyroidism during fetal life, infancy, and childhood if not treated?

Low TSH, high FT4, high FT3

What are the expected laboratory findings in primary hyperthyroidism?

High TSH, low FT4, low FT3

What are the expected laboratory findings in primary hypothyroidism?

Antibodies block thyroid hormone production

What is the primary mechanism in some forms of hypothyroidism, not Graves' disease?

Thyroid stimulating immunoglobulins (TSI) act like TSH, binding to TSH receptors

What is the primary mechanism of Graves' disease?

Reduced number of thyroid cells

What is a potential cause of hypothyroidism?

Goiter

Enlarged thyroid gland

Thyroid may extend intrathoracic or retropharyngeal

What are some anatomical complications of a goiter seen on CT scan?

Thyroid cancers

Contrast-enhanced CT scan of the thyroid can help determine the extent, spread, and metastasis of what?

Higher sensitivity in determining lymph node involvement

What is an advantage of CT scan over ultrasound in the evaluation of thyroid cancer?

Monitor recurrence

After treatment for thyroid cancer, what can contrast-enhanced CT scan be used for?

Determine presence of nodules, risk for malignancy

What is the primary utility of thyroid ultrasound?

Determine presence of parenchymal disease

Besides nodules, what else can thyroid ultrasound help identify?

Heterogeneous parenchyma

What ultrasound finding may be a sign of either hyper- or hypothyroidism?

Increased vascularity

What Doppler ultrasound finding is often a sign of a hyperactive thyroid or an inflammatory process?

Antero-posterior dimension of each lobe > 2 cm

What thyroid ultrasound measurement is considered enlarged?

Isthmus < 0.5 cm

What is the normal measurement for the thyroid isthmus on ultrasound?

Normal parathyroid gland is usually not seen on imaging

What is a key imaging characteristic of normal parathyroid glands?

Pathologic

If a parathyroid gland is seen on imaging, what is it likely?

Hypoechoic than thyroid parenchyma

How does a parathyroid adenoma typically appear on ultrasound compared to the thyroid?

Sestamibi scan

What nuclear imaging technique is used for parathyroid imaging?

Parathyroid adenoma retain activity on late scans

What is a characteristic finding on a Sestamibi scan suggestive of a parathyroid adenoma?

CT and MRI

What other imaging modalities may be used as a problem-solving tool in parathyroid imaging?

Ectopic hyperplastic parathyroid gland corresponding to radiotracer retention on prior sestamibi scan

What might CT or MRI show in the context of a positive Sestamibi scan?

Most useful in pre-natal and neonates

In which populations is adrenal ultrasound most useful?

Hypoechoic structure at the superior pole of each kidney

How do normal adrenal glands appear on ultrasound in neonates?

Difficult to delineate in adults, unless pathologic

What is a limitation of adrenal ultrasound in adults?

Adrenal glands best seen in CT or MRI

What are the preferred imaging modalities for the adrenal glands in adults?

Include a delayed scan at 15 minutes to determine Adrenal CT washout (for adrenal adenoma)

What is a key component of an adrenal protocol CT scan?

Include in-phase and out-of-phase sequences to differentiate lipid-rich adenomas from non-lipid containing adenomas

What is a key component of an adrenal protocol MRI?

“Y” or a “V”

What is the typical appearance of the adrenal gland on CT?

Ultrasound

What is the usual initial imaging for suspected pancreatic pathology / lesions?

CT, Ultrasound, and MRI

What imaging modalities provide high-quality images of the pancreas?

Contrast-enhanced CT and MRI

What imaging modalities are excellent for the detection of pancreatic tumors / mass lesions?

Pancreatic protocol for CT (multiphasic)

What specific CT protocol is used for detailed pancreatic imaging?

ERCP and MRCP

What imaging techniques demonstrate the pancreatic duct?

< 3.0 cm (Head), < 2.5 cm (Body), < 2.0 cm (Tail)

What are the normal measurement ranges for the head, body, and tail of the pancreas on imaging?

Diabetogenic effect

What is a potential metabolic consequence of glucocorticoids related to blood sugar?

Peptic ulcerations

What is a potential gastrointestinal side effect of glucocorticoids?

Promotes visceral obesity

How do glucocorticoids affect fat distribution?

↓ Bone formation, ↓ Bone mass, Osteoporosis

What are potential effects of glucocorticoids on bone and calcium metabolism?

Bronchodilation

What is the effect of catecholamines on the respiratory system that might be clinically relevant in asthma?

Chronotropy, Inotropy, Dromotropy

What are the cardiac effects of catecholamines that are important in stress response and cardiac conditions?

Insulin resistance

What metabolic condition can be promoted by catecholamines, relevant in diabetes management?

Reduced motility

How do catecholamines affect gastrointestinal activity, potentially contributing to constipation in stress?