Pituitary gland: (A few examples)
GH hormone - overproduction - causes Gigantism - long bones continue to grow well into adulthood.
Conversely, underproduction causes Dwarfism.
Overproduction of ADH (Vasopressin) causes excessive water retention. Underproduction causes Diabetes insipidus - inadequate water resorption causing watery urine.
Addison's disease - the adrenal glands do not make enough cortisol. Cortisol controls blood pressure, and balances effect of insulin. The lack of cortisol results in weight loss, muscle fatigue and low blood pressure.
Hyperthyroidism, (Graves' disease) can result from increased levels of TSH from the anterior pituitary, or as a response to auto-immune antibodies to the TSH receptor. There is accelerated synthesis and iodination of colloid, and augmented endocytosis of colloid by the epithelial cells lining the follicles, which leads to increased levels of thyroid hormone. This results in enlarged thyroid,and an elevated metabolism. It is often associated by antibody-mediated inflammatory enlargement of the extrinsic eye muscles and intraorbital connective tissues, which makes the eyballs protrude.
In contrast, lack of iodine in the diet, results in low levels of thyroid hormone - this results in elevated production of TSH as part of a feedback response, and the thyroid glands enlarges (goitre). Underproduction of thyroid hormone in fetuses or in infancy can lead to mental retardation and stunted body growth (cretinism).