The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
A newspaper lead (or lede if you prefer) can do its job in one sentence, but with few exceptions, a paragraph will contain more than one sentence. The OWL site, aimed at college students, suggests a length of from three to five or more sentences.
As noted above, a paragraph needs to develop an idea or new aspect of an argument, and it is impossible to do this in just a sentence or two. It is usually recommended, therefore, that in typical student writing a paragraph should be a minimum of five or six sentences.