Endocrine Regulation MCQ

Endocrine physiology reaches the dental chair through a handful of patients you will see often: the diabetic, the patient on long-term steroids, and the person with thyroid or adrenal disease. Learn the axis (hypothalamus to pituitary to gland), the feedback that controls it, and you can predict the safety issues: epinephrine in the hyperthyroid patient, adrenal crisis in the steroid-dependent patient, and healing in the diabetic.

Hypothalamic-Pituitary Axis

• The hypothalamus releases controlling hormones that direct the anterior pituitary, which in turn signals the peripheral glands; this is the chain of command for most hormones.
• The anterior pituitary makes ACTH, TSH, growth hormone, prolactin, FSH, and LH. The posterior pituitary stores and releases ADH and oxytocin, which are actually made in the hypothalamus.
• Negative feedback keeps the axis in check: a high level of the end hormone (such as cortisol or thyroid hormone) suppresses the pituitary and hypothalamus above it.
• Growth hormone excess enlarges tissues; before the growth plates close it causes gigantism, and after they close it causes acromegaly, with a larger jaw, spaced teeth, and macroglossia.

Thyroid & Parathyroid

• TSH from the pituitary drives the thyroid to make T3 and T4 (iodine-containing), which set the body's metabolic rate.
• Hyperthyroidism (often Graves disease) causes weight loss, heat intolerance, tachycardia, tremor, and exophthalmos; thyroid storm is a life-threatening crisis precipitated by stress, infection, or surgery.
• Hypothyroidism causes fatigue, cold intolerance, weight gain, bradycardia, and dry skin, with heightened sensitivity to sedatives and opioids.
• Parathyroid hormone raises blood calcium (bone resorption, renal reabsorption, vitamin D activation) and lowers phosphate; calcitonin from thyroid C cells lowers calcium.

Adrenal Gland Hormones

• The adrenal cortex has three zones, remembered as salt, sugar, and sex: aldosterone (mineralocorticoid), cortisol (glucocorticoid), and androgens, from outer to inner.
• Cortisol is the stress hormone: it raises blood glucose, is anti-inflammatory and immunosuppressive, and is permissive for catecholamines to maintain blood pressure.
• The adrenal medulla secretes the catecholamines epinephrine and norepinephrine; a catecholamine-secreting tumor (pheochromocytoma) causes episodic hypertension, headache, palpitations, and sweating.
• Adrenal insufficiency (low cortisol) risks an adrenal crisis under stress; long-term exogenous steroids suppress the patient's own axis, which is the most common cause of this concern in dentistry.

Diabetes Mellitus

• Type 1 diabetes is autoimmune destruction of the pancreatic beta cells with an absolute lack of insulin; type 2 is insulin resistance with a relative deficiency, usually with obesity.
• Insulin lowers blood glucose by promoting uptake and storage; without enough effective insulin, glucose rises and, in type 1, ketones can accumulate.
• HbA1c reflects the average blood glucose over roughly the prior three months and is the standard measure of long-term control (a level of 6.5% or higher is diagnostic).
• Chronic hyperglycemia damages vessels and nerves and impairs immunity and healing; periodontitis is so common in diabetes it is called the sixth complication, and the relationship is bidirectional.