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Endocrinology is a medical specialty that deals with the endocrine system and the diseases and conditions that affect it. The endocrine system has to do with the regulation of hormones in the body, and these hormones affect certain bodily functions and activities such as growth and development, metabolism, sensory perception, sleep, tissue function, respiration, digestion, lactation, stress, mood, excretion, reproduction and movement.
The endocrine system consists of numerous glands that are situated in different parts of the body, and these glands secrete hormones directly into the bloodstream rather than into a duct system. These hormones have various modes of action and perform different duties in the body. A target organ can be affected by many hormones and one hormone can produce several effects on different organs.
An endocrinologist has to complete the following education and training programmes in order to qualify as a specialist physician:
- 5-6 years of a medical undergraduate degree.
- 1-2 years of internship training to be exposed to different medical and surgical disciplines.
- 4 years residency in internal medicine.
- 2 years fellowship training in endocrinology.
It can therefore take a doctor 12-14 years to become a qualified endocrinologist.
Hormones and Glands associated with Endocrinology
There are 3 different classes of hormones and these are based on their chemical structures.
These hormones are converted from cholesterol and are divided into 5 groups called mineralocorticoids, glucocorticoids, oestrogens, androgens and progestogens.
Peptide hormones include those secreted by the pituitary gland, ghrelin from the stomach, leptin from adipocytes and insulin from the pancreas.
The amines include the hormones adrenaline and noradrenaline (secreted by the adrenal glands), dopamine (which is a catecholamine secreted by the brain) and the thyroid hormones T3 and T4 (secreted by the thyroid gland).
Diseases managed by Endocrinologists
- Hyperthyroidism - due to Graves disease or a toxic multinodular goitre.
- Thyroiditis such as Hashimoto's thyroiditis.
- Thyroid cancer.
- Thyroid hormone resistance.
Glucose homeostasis disorders
- Type 1 diabetes and late onset type 1 diabetes.
- Type 2 diabetes.
- Gestational diabetes.
- Hypoglycemia - due to an insulinoma or other idiopathic causes.
Calcium homeostasis disorders
- Parathyroid gland disorders such as primary, secondary and tertiary hyperparathyroidism, hypoparathyroidism and pseudohypoparathyroidism.
Metabolic bone diseases
- Paget's disease.
Pituitary gland disorders
The anterior pituitary - hypopituitarism, pituitary tumours such as pituitary adenomas and prolactinomas, acromegaly (gigantism) and Cushing's disease.
The posterior pituitary - diabetes insipidus.
Adrenal gland disorders
- Cushing's syndrome - causing excess corticosteroid production primarily due to adrenal gland masses such as pheochromocytomas, and secondary to anterior pituitary tumours.
- Addison's syndrome - causing decreased corticosteroid production due to primary adrenal insufficiency.
Sex hormone disorders
- Disorders of sex development or intersex disorders such as gonadal dysgenesis, hermaphroditism and androgen insensitivity syndromes.
- Puberty disorders such as delayed or precocious puberty.
- Hypogonadism (due to gonadotropin deficiency) in genetic or chromosomal disorders such as Turner syndrome, Kallman syndrome and Klinefelter syndrome. This also occurs in acquired disorders such as testicular and ovarian failure (premature menopause).
Other tumours of the endocrine glands
- Multiple endocrine neoplasias such as in MEN syndrome types 1, 2a and 2b.
- Carcinoid syndrome.