Thyroid Disorders: Study Guide

• Study notes on common thyroid disorders

Thyroid Disorders

• The thyroid gland is responsible for regulating metabolism through the production of hormones like T3, T4, and calcitonin
• Thyroid disorders include hypothyroidism, hyperthyroidism, goiter, and thyroid nodules

Hypothyroidism

• A condition where the thyroid gland does not produce sufficient T3 and T4, leading to a slow metabolism
• Causes include Hashimoto’s Thyroiditis (autoimmune, most common), iodine deficiency, post-thyroidectomy or post-radioactive iodine therapy, and congenital hypothyroidism (cretinism in newborns)
• Signs and Symptoms include weight gain despite decreased appetite, cold intolerance, bradycardia, hypotension, fatigue, lethargy, depression, dry skin, brittle nails, hair thinning, and constipation
• Goiter may occur as a compensatory response to thyroid enlargement.
• Myxedema Coma is a life-threatening complication and a severe form of hypothyroidism
• This can lead to severe bradycardia and hypotension, hypothermia, hypoventilation, respiratory failure, and coma with multi-organ failure
• Treatment includes lifelong replacement therapy with levothyroxine (Synthroid), monitoring TSH levels to adjust dosage, avoidance of sedatives and narcotics due to the risk of respiratory depression, and increasing fiber and fluids to alleviate constipation

Hyperthyroidism

• The overproduction of T3 and T4, leading to an increased metabolic rate
• Graves’ Disease is an autoimmune disorder and most common cause, where the thyroid gland is attacked, leading to excess production of thyroid hormone
• Signs and Symptoms include weight loss despite increased appetite, heat intolerance, tremors, exophthalmos (bulging eyes), goiter, tachycardia, and nervousness
• Radioactive Iodine Uptake (RAIU) Scan shows high uptake in Graves’ disease
• Thyroid Storm is a life-threatening complication and a medical emergency triggered by infection, surgery, or stress
• This leads to extreme hyperthermia (> 102°F), severe tachycardia (can lead to heart failure), hypertension leading to shock, delirium, seizures, and coma
• Treatment includes antithyroid medications like Methimazole (preferred) or Propylthiouracil (PTU for pregnancy), Beta-Blockers (Propranolol) to control tachycardia and anxiety, Radioactive Iodine Therapy (RAI) to shrink thyroid tissue, and thyroidectomy for severe or unresponsive cases
• Goiter is thyroid gland enlargement and can be caused by iodine deficiency or hormonal imbalance

Parathyroid Disorders

• Disorders that affect calcium and phosphorus balance via parathyroid hormone (PTH)

Hyperparathyroidism

• A condition where the parathyroid glands overproduce PTH, leading to high calcium levels (hypercalcemia)
• Causes include primary hyperparathyroidism (parathyroid adenoma or tumor), secondary hyperparathyroidism (chronic kidney disease (CKD), vitamin D deficiency), and tertiary hyperparathyroidism (persistent stimulation after kidney transplant)
• Signs and Symptoms include bone pain and fractures (calcium loss from bones leading to osteoporosis), kidney stones (calcium buildup in kidneys), psychiatric symptoms (depression, confusion), and GI issues (nausea, constipation, abdominal pain)
• Diagnosis includes elevated PTH and serum calcium levels, and decreased phosphorus levels
• Treatment includes parathyroidectomy (surgical removal of adenoma), hydration (to prevent kidney stones), bisphosphonates (alendronate) to prevent bone loss, and calcimimetics (cinacalcet) to lower calcium levels

Hypoparathyroidism

• A condition where the parathyroid glands produce too little PTH, leading to hypocalcemia (low calcium levels)
• Causes include post-thyroidectomy (most common cause), autoimmune destruction, and genetic disorders
• Signs and Symptoms ("Low Calcium = CATS") include convulsions, muscle spasms, arrhythmias (prolonged QT interval), tetany (Chvostek’s & Trousseau’s signs), seizures, stridor, and paresthesia (tingling in fingers/lips)
• Diagnosis includes decreased PTH and calcium levels, and increased phosphorus levels
• Treatment includes calcium supplements (IV calcium gluconate for severe cases), vitamin D (calcitriol) to enhance calcium absorption, and thiazide diuretics to reduce calcium excretion

Adrenal Disorders

• Are due to the adrenal glands, located on top of the kidneys
• The adrenal glands are responsible for hormone production including cortisol, aldosterone, and catecholamines (epinephrine and norepinephrine)
• Adrenal disorders can cause significant metabolic, cardiovascular, and immune system dysfunctions

Cushing’s Syndrome

• Characterized by excess cortisol, leading to weight gain, moon face, hyperglycemia, and hypertension (hyperadrenalism)
• Causes can be exogenous (prolonged steroid use like prednisone) or endogenous
• Endogenous causes can be Cushing’s Disease (pituitary tumor secreting excess ACTH), adrenal tumors (secrete excess cortisol), or ectopic ACTH syndrome (tumors like lung cancer producing ACTH)
• Signs and Symptoms include moon face, buffalo hump, truncal obesity, thin skin, easy bruising, purple striae (stretch marks), muscle wasting, osteoporosis, hypertension, hyperglycemia (diabetes risk), frequent infections (immunosuppression), and hirsutism (excess hair growth in women)
• Diagnosis includes a 24-hour urine cortisol test (elevated cortisol levels), dexamethasone suppression test (no suppression indicates Cushing’s), and serum cortisol & ACTH levels (to distinguish pituitary vs. adrenal cause)
• Treatment depends on the cause
• If caused by steroids, gradual tapering off steroids
• If caused by a tumor, surgery like adrenalectomy or pituitary tumor removal, or medications like ketoconazole or metyrapone to lower cortisol levels

Addison’s Disease

• A chronic disorder the adrenal glands don't produce enough cortisol and/or aldosterone
• Causes include autoimmune destruction of the adrenal glands, pituitary dysfunction (low ACTH production), hypothalamic dysfunction (low CRH production), tuberculosis, fungal infections, and abrupt steroid withdrawal
• Signs and Symptoms include fatigue, muscle weakness, weight loss, anorexia, and hypotension (due to low aldosterone, leading to sodium loss)
• There can be hyperpigmentation (bronze skin due to high ACTH levels in primary Addison’s), hypoglycemia, hyponatremia & hyperkalemia (due to low aldosterone), and salt cravings
• Diagnosis includes ACTH stimulation test (measures cortisol response to ACTH), serum cortisol levels (low in Addison’s), and electrolyte imbalances (decreased Na+ and glucose, increased K+)
• Treatment includes lifelong steroid replacement (hydrocortisone, prednisone), fludrocortisone (florinef) for aldosterone replacement, increased salt intake (especially during hot weather or exercise), and avoiding abrupt steroid withdrawal to prevent adrenal crisis
• Adrenal Crisis (Addisonian Crisis) is a life-threatening condition due to sudden cortisol deficiency, triggered by stress, infection, trauma, or abrupt steroid withdrawal which can results in severe hypotension, dehydration, confusion, and shock
• Management includes administering IV hydrocortisone immediately

Hyperaldosteronism (Conn’s Syndrome)

• Is due to excessive secretion of aldosterone, leading to hypertension and electrolyte imbalances
• Causes include adrenal adenoma (tumor) – most common, bilateral adrenal hyperplasia, and kidney disease
• Signs and Symptoms include hypertension (severe, resistant to meds), hypokalemia (muscle weakness, arrhythmias, polyuria), metabolic alkalosis (↑ HCO₃), headaches, and nocturia with fatigue
• Diagnosis includes serum aldosterone & renin ratio (↑ aldosterone, ↓ renin), and CT scan (detects adrenal tumors)
• Treatment includes spironolactone (aldactone) as an aldosterone antagonist, and adrenalectomy (if a tumor is present)

Pheochromocytoma

• A rare, life-threatening tumor of the adrenal medulla that causes excessive release of epinephrine & norepinephrine
• The tumor causes excessive catecholamine release, leading to hypertension and palpitations
• Signs & Symptoms (5 P's) include paroxysmal hypertension (severe, episodic), palpitations (tachycardia, arrhythmias), profuse sweating (diaphoresis), pounding headache, and pallor (or flushing)
• Other symptoms: tremors, weight loss, anxiety, and hyperglycemia
• Diagnosis includes a 24-hour urine test for metanephrines & catecholamines, plasma metanephrine test (most sensitive), and MRI/CT scan (detects adrenal tumor)
• Treatment includes pre-op alpha-blockers (phenoxybenzamine) to control BP, surgical removal of the tumor (adrenalectomy), and control BP with antihypertensives

Pituitary Disorders

• Are due to the pituitary gland which regulates various hormones affecting multiple organs

Acromegaly/Gigantism

• Acromegaly occurs in adults after growth plate closure
• Characterized by enlarged hands, feet, facial bones, and soft tissues
• Gigantism occurs in children before growth plate closure -Leads to excessive height and size
• Cause is typically a pituitary adenoma (benign tumor) that overproduces GH
• Signs & Symptoms include enlarged hands, feet, and facial features (acromegaly), excessive height and rapid growth in children (gigantism), joint pain, thickened skin, enlarged organs (heart, liver), headache, and vision problems (pressure from tumor)
• Complications include cardiovascular disease (hypertension, cardiomyopathy), diabetes mellitus (due to insulin resistance), and arthritis and joint deformities
• Treatment includes surgery like transsphenoidal hypophysectomy to remove the pituitary tumor, medications like octreotide (sandostatin) to inhibit GH secretion or pegvisomant to block GH effects, and radiation therapy if surgery is ineffective
• Nursing Interventions include monitoring blood glucose levels because of the risk of diabetes, assessing for signs of increased ICP (headache, vision loss), and post-surgery care (avoid coughing, sneezing, bending forward to reduce CSF leak risk and monitor for meningitis with fever and stiff neck)

Diabetes Insipidus (DI)

• Characterized by excessive urination (polyuria) and dehydration due to low antidiuretic hormone (ADH) levels
• Types include neurogenic DI which is caused by damage to the hypothalamus or pituitary gland (trauma, tumor, surgery) and nephrogenic DI where kidneys do not respond to ADH (due to lithium toxicity or kidney disease)
• Signs & Symptoms include polyuria (excess urine output > 3L/day), polydipsia (excessive thirst), hypotension, dehydration, tachycardia, and dilute urine (low specific gravity 1.005)
• Complications include severe dehydration & electrolyte imbalances (hypernatremia) and hypovolemic shock
• Diagnostic Tests include water deprivation test (differentiates between neurogenic and nephrogenic DI) and urine specific gravity & osmolality (low in DI)
• Treatment for neurogenic DI is desmopressin (DDAVP) - a synthetic ADH
• Treatmente for nephrogenic DI is thiazide diuretics (HCTZ) which reduces urine output and fluid replacement therapy
• Nursing Interventions include monitoring I&O (daily weights, urine output), encouraging hydration and monitoring for dehydration signs, and educating on lifelong medication adherence for neurogenic D

SIADH (Syndrome of Inappropriate ADH Secretion)

• Characterized by water retention and dilutional hyponatremia due to excess ADH
• Causes include lung cancer which is the most common cause in addition to CNS disorders (stroke, head trauma, infections), and medications like SSRIs and carbamazepine
• Signs & Symptoms include fluid retention, weight gain (without edema), an hyponatremia (confusion, seizures, muscle cramps)
• There is a low urine output (concentrated urine)
• Seizures and comas can result as a consequence of severe hyponatremia which can lead to cerebral edema
• Treatment includes Fluid restriction (100 mg/dL)

Treatment

• Weight loss, dietary changes, and exercise as well as using statins (for cholesterol), and if needed, antihypertensives

Polycystic Ovary Syndrome (PCOS)

• A hormonal imbalance condition that causes irregular cycles, infertility, and insulin resistance