[The pituitary gland] is known as the "master gland" because it exerts control over all of the other glands of the endocrine system. ... The Pituitary gland is made up of two separate glands: the Anterior lobe which is an outgrowth of the pharynx, and the Posterior lobe which is an outgrowth of the brain composed of neural (nerve) tissue. ... The Posterior Lobe of the Pituitary Gland (or neurophpophysis) stores and releases hormones secreted by the hypothalamus section of the brain.... ("The Endocrine System," endocrine system consists of several glands, some of which being controlled by the pituitary endocrine gland and the hypothalamus, the first of the two being more autonomous. Secretions of thyroid gland, adrenal and gonads (ovaries and testes) depend tightly by pituitary hormones. Pituitary hormones are in turn under the control of the hypothalamus.The other endocrine glands are parathyroid glands, adrenal glands and endocrine pancreas. The endocrine system has the particularity of self-control, thanks to the control of hypothalamic-pituitary corresponding hormonal secretions. The pituitary is controlled by the hypothalamus, which is a central nervous system structure.Pituitary secretions are CRF (corticotropin releasing factor), TRH (thyrotrophin releasing hormone), Gn-RH (gonadotrophin releasing hormone), LH-RH, (luteinizing releasing hormone), GH-RH (growth hormone-releasing hormone inhibiting) , and dopamine, partly secreted by the hypothalamus, which controls the secretion of prolactin. Hope I helped You :)

The person will easily get affected by diseases and will have a abnormality in transporting cells via blood vessels.
here is the answer for no.2
According to my book, a thymus gland is a small gland located in the neck a few inches below the thyroid. One of its main function is to identify invading bacteria and viruses. Therefore, the thymus gland is a big help not only on our immune system, but also to our human system.
here for no.1 hope it helps