Endocrine glands: Endocrine organs, called glands, secrete hormones into the bloodstream. Hormones affect the activity of target sites that are often located far from the site of release. Exocrine organs direct the function of their target sites by releasing their active.
Human endocrine system: The major endocrine organs include the hypothalamus and the hypophysis, or pituitary gland. Other endocrine glands within the body include: thyroid, parathyroids, adrenals, pancreas, ovaries, and testes.
The Menstrual Cycle and Pregnancy
From puberty to menopause, hormonal interplay between the hypothalamus, pituitary, and ovaries results in the monthly menstrual cycle, which has four distinct phases: follicular phase and the luteal phase.
Fertilization on or around day 14 of the menstrual cycle is followed by implantation of the
zygote and development of the placenta.
Mechanisms of hormone action
Hormones may be grouped into three major categories, depending on their chemical
- Peptide hormones include simple peptides like ADH,
- Steroid hormones include fat derived compounds like estrogen and
- Amino acid-derived hormones include epinephrine and T4.