Thyroid disorders include hypo- and hyperthyroidism, Hashimoto's disease, Graves’ disease, goiter, and thyroiditis.

Hypothyroidism

Primary hypothyroidism is a condition characterized by the failure of the thyroid gland to produce sufficient thyroid hormone.

Secondary and tertiary hypothyroidism are both referred to as central hypothyroidism. The pathology of secondary hypothyroidism lies in the pituitary gland and its failure to secrete TSH. Tertiary hypothyroidism is caused by a deficiency in the hypothalamus, which fails to regulate the pituitary gland through the secretion of TRH.

Subclinical hypothyroidism is a form of hypothyroidism with minimal or no obvious signs and symptoms of a hypometabolic state. However, there is an elevated TSH despite normal T4 levels. There is controversy regarding the management of this subtype of the disease

Hyperthyroidism

Hyperthyroidism refers to conditions caused by excessive thyroid hormone produced by the thyroid gland.

The most common causes of hyperthyroidism are Graves' disease, toxic multinodular goiter, toxic uninodular goiter, and thyroiditis.

Less common causes of hyperthyroidism are thyroid-stimulating hormone (TSH)-producing tumors, pituitary resistance to thyroid hormone, trophoblastic disease, and iodine ingestion

Signs and symptoms generally result from stimulation of the adrenergic nervous system

Parathyroid disorders such as hyperparathyroidism often leads to significant hypercalcaemia.

Primary hyperparathyroidism

• Primary hyperparathyroidism is a common disease that occurs when one or more of the parathyroid glands become overactive. This leads to the overproduction of parathyroid hormone (PTH), resulting in an abnormal elevation in serum calcium
• Patients with primary disease are always hypercalcemic
• In 85% of patients with primary hyperparathyroidism, hypercalcemia is due to the benign enlargement of in most cases a single parathyroid gland (parathyroid adenoma). Adenomas involve multiple glands less frequently
• Loss of sensitivity of these proliferating chief cells to normal extracellular calcium concentrations occurs
• Hypercalcemia is usually discovered during a routine serum chemistry profile
• Some combination of headaches, fatigue, anorexia, nausea, paresthesias, muscular weakness, pain in the extremities, pain in the abdomen, and other such nonspecific symptoms appears to be the most common presentation of the hypercalcemia associated with primary hyperparathyroidism
• Symptoms of hypercalcemia are vague and may be similar to symptoms of depression, irritable bowel syndrome, fibromyalgia, or stress reaction

Secondary and tertiary hyperparathyroidism

• Secondary and tertiary hyperparathyroidism occur in patients with kidney failure or severe vitamin D deficiency and are characterized by enlargement of all four parathyroid glands (hyperplasia)
• In secondary hyperparathyroidism, the vast majority of cases demonstrate only chief cell hyperplasia
• Patients with secondary disease are almost always normocalcemic
• Tertiary hyperparathyroidism occurs when parathyroid hyperplasia becomes so severe that removal of the underlying cause does not eliminate the stimulus for PTH secretion and hypertrophic chief cells become autonomous
• Approx. 20% of patients with hyperparathyroidism have kidney stones (whereas only 2-3% of patients with kidney stones have hyperparathyroidism)