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.
The parathyroid glands are four tiny glands located in the neck. These glands control the level of calcium in the blood. If one or more of the glands is too active, it can cause a high blood calcium level. This is called hyperparathyroidism.