Endocrinology — Find Specialists & Top Hospitals Worldwide | MyMedicPlus

Endocrinology is the branch of internal medicine concerned with the endocrine system — the network of glands and organs that produce, store, and secrete hormones directly into the bloodstream to regulate vital body functions. These include metabolism, growth and development, reproductive function, stress response, fluid and electrolyte balance, and calcium and bone metabolism. Endocrinologists are physicians who specialise in diagnosing and treating hormonal imbalances and the diseases of the endocrine glands.

The major endocrine glands include the hypothalamus and pituitary gland (the master regulators of the endocrine system), the thyroid and parathyroid glands, the adrenal glands, the endocrine pancreas (insulin-producing islets of Langerhans), the gonads (ovaries and testes), and the pineal gland. Disease affecting any of these glands — through hormone excess, deficiency, or failure of regulation — falls within the scope of endocrinology.

Endocrinology overlaps significantly with other specialties. Diabetes mellitus is managed jointly by endocrinologists and primary care physicians, with diabetology emerging as a subspecialty in high-prevalence countries. Reproductive endocrinology and infertility (REI) is practised as a subspecialty of obstetrics and gynaecology rather than medical endocrinology. Neuroendocrinology bridges endocrinology and neurology in the management of pituitary and hypothalamic disorders. Paediatric endocrinology addresses growth disorders, precocious or delayed puberty, congenital adrenal hyperplasia, and childhood diabetes.

Endocrinologists manage a broad spectrum of hormonal and metabolic conditions:

• Hypothyroidism: Underactive thyroid gland causing fatigue, weight gain, cold intolerance, constipation, and depression; most commonly due to Hashimoto thyroiditis (autoimmune) or post-thyroidectomy; treated with levothyroxine replacement.
• Hyperthyroidism and Graves disease: Overactive thyroid causing weight loss, palpitations, heat intolerance, tremor, and exophthalmos (in Graves disease); treated with antithyroid drugs, radioactive iodine, or thyroidectomy.
• Thyroid nodules and thyroid cancer: Solid or cystic thyroid lesions evaluated by ultrasound and fine-needle aspiration biopsy; papillary and follicular thyroid cancers are managed by endocrinologists in coordination with thyroid surgeons and nuclear medicine.
• Type 1 and type 2 diabetes mellitus: Endocrinologists manage complex diabetes, insulin regimens, and complication surveillance (see diabetology section for detail).
• Adrenal insufficiency (Addison disease): Primary adrenal failure causing cortisol and aldosterone deficiency, requiring lifelong glucocorticoid and mineralocorticoid replacement with sick-day rules education.
• Cushing syndrome: Excess cortisol causing central obesity, hypertension, hyperglycaemia, easy bruising, and purple striae; caused by pituitary adenoma (Cushing disease), adrenal tumour, or ectopic ACTH secretion.
• Pheochromocytoma and paraganglioma: Rare catecholamine-secreting adrenal or extra-adrenal tumours causing hypertensive crises, headache, palpitations, and sweating; require specialised biochemical diagnosis and surgical management.
• Pituitary adenomas: Benign pituitary tumours that may cause hormone excess (prolactinoma, acromegaly, Cushing disease) or mass effects (visual field defects, hypopituitarism); managed medically, surgically, or with radiation.
• Acromegaly: Excess growth hormone from a pituitary adenoma causing enlargement of hands, feet, and facial features, joint disease, and cardiovascular complications.
• Polycystic ovary syndrome (PCOS): The most common endocrine disorder in women of reproductive age, causing irregular periods, androgen excess, polycystic ovaries, and insulin resistance.
• Osteoporosis: Metabolic bone disease of reduced bone mineral density leading to fragility fractures; managed with bisphosphonates, denosumab, romosozumab, or teriparatide depending on fracture risk.
• Primary hyperparathyroidism: Excess parathyroid hormone from an adenoma causing hypercalcaemia, kidney stones, osteoporosis, and symptoms of hypercalcaemia; definitive treatment is surgical parathyroidectomy.

Endocrinologists use specialised diagnostic tests and procedures to evaluate the function of endocrine glands:

• Thyroid function tests: Measurement of TSH (thyroid-stimulating hormone) and free T4, free T3 to assess thyroid status; TSH is the most sensitive first-line screening test for thyroid dysfunction.
• Thyroid ultrasound: High-resolution imaging of the thyroid gland to characterise nodules (size, echogenicity, vascularity, calcifications) and guide biopsy decisions using ACR TI-RADS or ATA risk stratification systems.
• Fine-needle aspiration biopsy (FNAB) of thyroid nodules: Ultrasound-guided aspiration of thyroid nodule cells for cytological examination to differentiate benign from malignant nodules; the cornerstone of thyroid nodule evaluation.
• DEXA bone density scanning: Dual-energy X-ray absorptiometry measures bone mineral density at the lumbar spine and femoral neck; T-scores guide osteoporosis diagnosis and treatment decisions using FRAX fracture risk calculator.
• Dynamic hormonal stimulation and suppression tests: Insulin tolerance test (ITT) for growth hormone and cortisol reserve; overnight dexamethasone suppression test and 24-hour urine free cortisol for Cushing syndrome; oral glucose tolerance test (OGTT) for acromegaly diagnosis.
• ACTH stimulation test (Synacthen/Cosyntropin test): Gold standard for diagnosing adrenal insufficiency — measures cortisol response to synthetic ACTH stimulation.
• 24-hour urine and plasma catecholamines and metanephrines: Biochemical diagnosis of pheochromocytoma and paraganglioma using plasma-free or urine fractionated metanephrines.
• Radioactive iodine therapy (RAI): Iodine-131 administered orally for Graves hyperthyroidism (to reduce thyroid activity) or differentiated thyroid cancer (to ablate residual thyroid tissue and metastases after thyroidectomy).
• Pituitary function testing: Assessment of GH, LH, FSH, TSH, ACTH, and prolactin axes through baseline measurements and dynamic stimulation tests for suspected hypopituitarism.

Many endocrine conditions — particularly simple hypothyroidism treated with levothyroxine and well-controlled type 2 diabetes — are managed effectively by primary care physicians. However, several specific situations warrant referral to an endocrinologist.

Thyroid conditions requiring specialist evaluation: Any thyroid nodule greater than 1 cm detected incidentally or clinically warrants ultrasound and potentially biopsy by an endocrinologist. Hyperthyroidism, especially Graves disease with ophthalmopathy, thyroid cancer management, and difficulty achieving stable thyroid hormone levels despite multiple medication adjustments all benefit from specialist care.

Adrenal disease: Any patient with incidentally discovered adrenal mass (incidentaloma) on imaging, suspected Cushing syndrome (round face, central obesity, stretch marks, unexplained hypertension and diabetes), clinical features of adrenal insufficiency, or uncontrolled hypertension with suspected hyperaldosteronism warrants endocrinology evaluation.

Pituitary disease: Visual field defects, persistent headaches, and galactorrhoea (non-puerperal milk secretion) may indicate a pituitary tumour and require urgent MRI and endocrinology review. Patients with elevated IGF-1 and features of acromegaly should be referred promptly.

Metabolic bone and calcium disorders: Unexplained osteoporosis in men, premenopausal women, or those under 65; recurrent kidney stones; persistent hypercalcaemia; or low serum 25-hydroxyvitamin D not correcting with supplementation may signal an underlying endocrine disorder requiring specialist assessment. Refer women with PCOS if they are trying to conceive, have metabolic syndrome, or require guidance on insulin sensitisation and ovulation induction.

Endocrinology training begins with a 4-year medical degree (MD or DO), followed by a 3-year internal medicine residency providing comprehensive exposure to all adult organ systems. Following residency and passing the ABIM internal medicine board certification, physicians apply for a 2–3 year fellowship in endocrinology, diabetes, and metabolism.

During fellowship, trainees rotate through inpatient endocrine consultations, diabetes clinic, thyroid nodule and ultrasound clinics, bone and calcium clinics, pituitary and adrenal clinics, and reproductive endocrinology. Research is an integral component of most fellowship programmes — particularly at academic medical centres — as the field is rapidly evolving with new medications, technologies, and diagnostic criteria.

Board certification in endocrinology, diabetes, and metabolism is conferred by the American Board of Internal Medicine (ABIM) following successful completion of the subspecialty written examination. Recertification every 10 years ensures ongoing currency with evidence-based practice. Subspecialty training in paediatric endocrinology leads to separate ABP board certification.

In the UK, the endocrinology and diabetes training pathway runs for 5 years under the JRCPTB, leading to a Certificate of Completion of Training (CCT) in Endocrinology and Diabetes. Subspecialty interest certificates are available in diabetes technology, thyroid cancer, pituitary disease, and reproductive endocrinology through the Society for Endocrinology and the Association of British Clinical Diabetologists.

Your primary care physician will refer you to an endocrinologist based on abnormal hormonal blood tests, clinical findings, or imaging results suggesting an endocrine disorder. Verify board certification through the ABIM online verification tool. For specific conditions such as pituitary tumours, rare adrenal disorders, or thyroid cancer, seek an endocrinologist at a centre with a dedicated multidisciplinary team — including endocrine surgeons, nuclear medicine physicians, and neuroradiologists — as outcomes are significantly better at high-volume specialist centres.

For your first appointment, bring all recent laboratory results (including thyroid function tests, cortisol, calcium, and HbA1c if relevant), any relevant imaging reports, a complete medication list, and a detailed symptom history. Many endocrine conditions have overlapping symptoms — fatigue, weight change, and mood disturbance — and a thorough history is essential to guide targeted investigation. Endocrine conditions often require long-term monitoring: thyroid disease, diabetes, adrenal insufficiency, and osteoporosis are lifelong conditions requiring regular specialist follow-up and treatment adjustment.