While discussing hormonal control of bone formation, one should note that which hormone lowers blood calcium levels and decreases bone resorption?

The hormone that helps bone calcification and new formation or osteoblastic stimulation is osteocalcin par excellence, although there are others that collaborate with bone synthesis such as vitamin D, thyroid hormones, and even testosterone.

Explanation:

The neoformation, calcification or decalcification of the bone is regulated by the bone cells that are the osteoclasts and osteblasts.

These cells capture the amount of calcium in the blood, that is, calcium, and according to its values they decide to calcify bone, or desalcify it by means of bone resorption.

The body's calcium balance is an ideal balance between the endocrine system, the degree of calcium and bone cells.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.