Human Endocrine System

Calcitriol is the active form of Vitamin D and enhances calcium absorption from the intestine, thus increasing blood calcium levels. It works in coordination with PTH (parathyroid hormone).

Cortisol regulates blood pressure and glucose metabolism. Low cortisol levels can lead to hypotension (low BP), while excess cortisol increases blood glucose, leading to hyperglycemia. Hence, both statements are correct.

Parathyroid hormone (PTH) actually increases calcium levels in the blood by stimulating bone resorption, increasing calcium reabsorption in kidneys, and promoting activation of vitamin D for calcium absorption in the intestine.
Thus, statement (2) is incorrect. All other statements are correct: the pituitary sits in the sella turcica, thymosin aids T-cell maturation, and zona fasciculata is the middle adrenal cortex layer.

Diabetes mellitus results from lack of insulin (Type 1) or insulin resistance (Type 2). Insulin is produced by beta cells in the pancreas. The thyroid, adrenal, and pituitary produce other hormones unrelated to blood glucose control.

Erythropoietin is a glycoprotein hormone secreted primarily by the kidneys in response to hypoxia (low oxygen levels). It stimulates the bone marrow to increase red blood cell production to improve oxygen transport in the body.

- A) Insulin — Protein (IV)
- B) Estrogen — Steroid (I)
- C) Oxytocin — Peptide (II)
- D) Thyroxine — Amine (III)