Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean; but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans.
Euthyroid is the state of having normal thyroid gland function. Examples of a nonfunctioning thyroid gland may be hypothyroidism, hyperthyroidism, or thyroiditis.
Parathormone, also called parathyroid hormone, substance produced and secreted by the parathyroid glands that regulates serum calcium concentration. Under the microscope the parathormone-producing cells, called chief cells, isolated from the parathyroid glands, occur in sheets interspersed with areas of fatty tissue. Occasionally the cells are arranged in follicles similar to but smaller than those present in the thyroid gland.