The human endocrine system is a complex network of glands that produce and regulate hormones, essential for maintaining homeostasis. Understanding endocrine disorders is crucial for medical professionals preparing for the Medical Council of Canada Qualifying Examination (MCCQE). This blog will delve into key endocrine disorders, their pathophysiology, clinical manifestations, diagnosis, and management.
Overview of the Endocrine System
The endocrine system comprises glands such as the pituitary, thyroid, parathyroid, adrenal glands, pancreas, and gonads (testes and ovaries). These glands secrete hormones that regulate metabolism, growth, reproduction, and other vital functions. Hormonal imbalances can lead to significant health issues, making endocrine disorders an essential area of study for the MCCQE.
Common Endocrine Disorders
1. Diabetes Mellitus
One of the most prevalent endocrine disorders, diabetes mellitus (DM), results from insufficient insulin production or resistance to insulin. It is classified into:
- Type 1 Diabetes Mellitus (T1DM): An autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency.
- Type 2 Diabetes Mellitus (T2DM): Characterized by insulin resistance and relative insulin deficiency.
Clinical Presentation
- Polyuria, polydipsia, polyphagia
- Unintentional weight loss (T1DM)
- Fatigue and blurred vision
- Increased risk of infections
Diagnosis
- Fasting plasma glucose (FPG) ≥ 7.0 mmol/L
- Hemoglobin A1C ≥ 6.5%
- Random plasma glucose ≥ 11.1 mmol/L with symptoms
- Oral glucose tolerance test (OGTT) ≥ 11.1 mmol/L
Management
- T1DM: Insulin therapy
- T2DM: Lifestyle modification, oral hypoglycemics (metformin), insulin (if necessary)
2. Hypothyroidism & Hyperthyroidism
The thyroid gland plays a key role in metabolism regulation. Disorders include hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid).
Hypothyroidism
- Causes: Hashimoto’s thyroiditis (autoimmune), iodine deficiency, post-thyroidectomy
- Symptoms: Fatigue, weight gain, bradycardia, cold intolerance, constipation
- Diagnosis: High TSH, low free T4
- Management: Levothyroxine replacement therapy
Hyperthyroidism
- Causes: Graves’ disease, toxic multinodular goiter
- Symptoms: Tachycardia, weight loss, heat intolerance, tremors, exophthalmos (Graves’ disease)
- Diagnosis: Low TSH, high free T4, positive TSH receptor antibodies (Graves’ disease)
- Management: Beta-blockers, antithyroid drugs (methimazole, propylthiouracil), radioactive iodine therapy, surgery
3. Cushing’s Syndrome & Addison’s Disease
The adrenal glands produce hormones such as cortisol and aldosterone, vital for metabolism and stress response.
Cushing’s Syndrome (Excess Cortisol)
- Causes: Pituitary adenoma (Cushing’s disease), exogenous corticosteroids, adrenal tumors
- Symptoms: Central obesity, moon face, buffalo hump, hypertension, glucose intolerance
- Diagnosis: 24-hour urinary free cortisol, dexamethasone suppression test
- Management: Surgical removal of tumors, corticosteroid tapering
Addison’s Disease (Adrenal Insufficiency)
- Causes: Autoimmune destruction, tuberculosis, adrenal hemorrhage
- Symptoms: Fatigue, weight loss, hypotension, hyperpigmentation
- Diagnosis: Low cortisol, high ACTH, positive ACTH stimulation test
- Management: Lifelong corticosteroid replacement (hydrocortisone, fludrocortisone)
4. Hyperparathyroidism & Hypoparathyroidism
The parathyroid glands regulate calcium homeostasis.
Hyperparathyroidism
- Causes: Parathyroid adenoma, chronic kidney disease
- Symptoms: Kidney stones, osteoporosis, muscle weakness, polyuria
- Diagnosis: Elevated serum calcium and PTH, low phosphorus
- Management: Surgical removal (parathyroidectomy), bisphosphonates
Hypoparathyroidism
- Causes: Post-thyroidectomy, autoimmune destruction
- Symptoms: Tetany, muscle cramps, paresthesia, Chvostek’s & Trousseau’s signs
- Diagnosis: Low calcium, low PTH, high phosphorus
- Management: Calcium and vitamin D supplementation
5. Polycystic Ovary Syndrome (PCOS)
A common endocrine disorder affecting reproductive-age women.
Causes & Pathophysiology
- Hyperandrogenism, insulin resistance, ovarian dysfunction
Clinical Features
- Irregular menstrual cycles
- Hirsutism, acne
- Obesity, insulin resistance
Diagnosis
- Rotterdam criteria (2 out of 3): Oligo/anovulation, hyperandrogenism, polycystic ovaries on ultrasound
Management
- Lifestyle changes, oral contraceptives, metformin, anti-androgens (spironolactone)
6. Acromegaly & Growth Hormone Deficiency
Growth hormone (GH) disorders arise from the pituitary gland.
Acromegaly (Excess GH in Adults)
- Causes: Pituitary adenoma
- Symptoms: Enlarged hands, feet, facial features, hypertension, diabetes
- Diagnosis: Elevated IGF-1, failure of GH suppression on glucose tolerance test
- Management: Surgery, somatostatin analogs (octreotide), GH receptor antagonists
Growth Hormone Deficiency
- Causes: Congenital, pituitary damage
- Symptoms: Short stature, delayed puberty
- Diagnosis: Low IGF-1, failed GH stimulation test
- Management: GH replacement therapy
Table of Common Endocrine Disorders
| Disorder | Causes | Clinical Features | Diagnosis | Management |
|---|---|---|---|---|
| Diabetes Mellitus | T1DM: Autoimmune destruction of beta cells; T2DM: Insulin resistance | Polyuria, polydipsia, weight loss (T1DM), fatigue, blurred vision | Fasting plasma glucose ≥ 7.0 mmol/L, HbA1c ≥ 6.5% | T1DM: Insulin therapy; T2DM: Lifestyle changes, metformin, insulin if needed |
| Hypothyroidism | Hashimoto’s thyroiditis, iodine deficiency | Fatigue, weight gain, cold intolerance | High TSH, low free T4 | Levothyroxine |
| Hyperthyroidism | Graves’ disease, toxic multinodular goiter | Tachycardia, weight loss, exophthalmos | Low TSH, high free T4, TSH receptor antibodies | Beta-blockers, antithyroid drugs, radioactive iodine, surgery |
| Cushing’s Syndrome | Pituitary adenoma, corticosteroids | Moon face, obesity, hypertension | 24-hour urinary cortisol, dexamethasone suppression test | Surgery, corticosteroid tapering |
| Addison’s Disease | Autoimmune, TB, adrenal hemorrhage | Fatigue, weight loss, hypotension, hyperpigmentation | Low cortisol, high ACTH, ACTH stimulation test | Lifelong corticosteroid replacement |
| Hyperparathyroidism | Parathyroid adenoma, CKD | Kidney stones, osteoporosis | High calcium, high PTH, low phosphorus | Parathyroidectomy, bisphosphonates |
| Hypoparathyroidism | Post-thyroidectomy, autoimmune | Tetany, paresthesia, Chvostek’s & Trousseau’s signs | Low calcium, low PTH, high phosphorus | Calcium and vitamin D supplementation |
| Polycystic Ovary Syndrome (PCOS) | Hyperandrogenism, insulin resistance | Irregular menses, hirsutism, acne | Rotterdam criteria (2 of 3: oligo/anovulation, hyperandrogenism, polycystic ovaries) | Lifestyle changes, OCPs, metformin, spironolactone |
| Acromegaly | Pituitary adenoma | Enlarged hands, feet, facial features | High IGF-1, failed GH suppression on OGTT | Surgery, somatostatin analogs |
| Growth Hormone Deficiency | Congenital, pituitary damage | Short stature, delayed puberty | Low IGF-1, failed GH stimulation test | GH replacement therapy |
Comparison and Differences Between Key Endocrine Disorders
Diabetes Mellitus vs. Cushing’s Syndrome
| Feature | Diabetes Mellitus | Cushing’s Syndrome |
| Cause | T1DM: Autoimmune; T2DM: Insulin resistance | Excess cortisol production |
| Clinical Features | Polyuria, polydipsia, weight changes | Moon face, central obesity, striae |
| Diagnosis | Fasting plasma glucose, HbA1c | 24-hour urinary cortisol, dexamethasone suppression test |
| Management | Insulin, lifestyle changes, oral hypoglycemics | Surgery, steroid tapering |
Hypothyroidism vs. Hyperthyroidism
| Feature | Hypothyroidism | Hyperthyroidism |
| Cause | Hashimoto’s, iodine deficiency | Graves’ disease, toxic goiter |
| Clinical Features | Fatigue, weight gain, cold intolerance | Tachycardia, weight loss, heat intolerance |
| Diagnosis | High TSH, low free T4 | Low TSH, high free T4 |
| Management | Levothyroxine | Beta-blockers, antithyroid drugs, radioactive iodine |
Addison’s Disease vs. Cushing’s Syndrome
| Feature | Addison’s Disease | Cushing’s Syndrome |
| Cause | Adrenal insufficiency (autoimmune, TB) | Excess cortisol (pituitary/adrenal tumor, steroids) |
| Clinical Features | Fatigue, weight loss, hyperpigmentation | Moon face, obesity, hypertension |
| Diagnosis | Low cortisol, high ACTH | High cortisol, suppressed ACTH with dexamethasone test |
| Management | Lifelong corticosteroids | Surgery, steroid tapering |
Hyperparathyroidism vs. Hypoparathyroidism
| Feature | Hyperparathyroidism | Hypoparathyroidism |
| Cause | Parathyroid adenoma, CKD | Post-thyroidectomy, autoimmune |
| Clinical Features | Kidney stones, osteoporosis | Tetany, paresthesia, Chvostek’s & Trousseau’s signs |
| Diagnosis | High calcium, high PTH, low phosphorus | Low calcium, low PTH, high phosphorus |
| Management | Parathyroidectomy, bisphosphonates | Calcium and vitamin D supplementation |
Conclusion
Endocrine disorders are a crucial topic for the MCCQE, requiring a solid grasp of their pathophysiology, clinical presentation, diagnostic criteria, and management strategies. A comprehensive understanding helps physicians provide optimal care and successfully tackle exam questions. Continuous learning and practice with clinical vignettes will enhance MCCQE preparation, ensuring confidence in tackling endocrine-related questions.
By mastering these disorders, medical professionals will be better equipped to diagnose and treat endocrine conditions, improving patient outcomes and advancing their medical careers. Read more blog…
