There are two types of organization of the endocrine system: cerebropituitary type and pituitary-independent type.
Cerebropituitary type includes the brain cortex, hypothalamus, anterior pituitary, peripheral endocrine glands, and the target cells. The brain cortex exerts neurogenic influence on the hypothalamus which produces liberins or statins. The hypothalamic hormones are secreted into the pituitary portal system and affect trophocytes producing tropins (e.g. ACTH, gonadotropins). The latter are secreted into general circulation and reach the peripheral endocrine glands where they exert stimulating or inhibitory effect.
In the pituitary-independent system the pituitary stage is omitted. For example, parathyroid gland or beta-cells of the pancreas are not regulated by pituitary trophins.
Endocrinopathy can result from hormone deficiency, hormone excess, resistance to hormone action, or constitutive mutations that activate the hormone response systems in the absence of ligand.
DEFICIENCY STATES
With few exceptions (calcitonin), hormone deficiency results in pathological manifestations. The destructive processes that cause failure of the endocrine organs include:
• infections;
• tissue death due to infarction or inflammation;
• tumors;
• autoimmune processed hormones;
• dietary inadequacy;
• hereditary defects in hormone synthesis.
Hormone excess
With few exceptions (testosterone in men, progesterone in men and women) hormone excess causes pathological effects. Hormone may be overproduced by the gland due to adenoma, autoantibodies that mimic the action of tropins (as in the case of thyroid-stimulating immunoglobulins in hyperthyroidism), mutations in receptor-effector mechanisms that impair feedback. A second type of hormone excess results when a hormone is produced by a tissue (usually malignant) that does not synthesize it ordinarily (e.g. ACTH production by carcinoma of the lungi). A third type of hormone excess involves the overproduction of hormones in the peripheral tissues from circulating precursors.