Endocrine glands and hormones
Glands and their hormones
The hypothalamus controls the pituitary, the master gland. Anterior pituitary: growth hormone, TSH, ACTH, FSH, LH, prolactin. Posterior pituitary stores ADH and oxytocin, made in the hypothalamus. Thyroid: thyroxine (T3/T4), needing iodine, raises metabolic rate; calcitonin lowers blood calcium. Parathyroid: PTH raises blood calcium. Adrenal cortex: cortisol for stress and glucose, aldosterone for salt and water; adrenal medulla: adrenaline for emergencies. Pancreas: insulin from beta cells lowers blood glucose, glucagon from alpha cells raises it. Gonads: testosterone, oestrogen, progesterone. Pineal: melatonin for sleep rhythm. Thymus: immunity in children.
Feedback
Hormones act in tiny amounts and are regulated by negative feedback - high thyroxine suppresses TSH.
Disorders
Excess growth hormone before puberty gives gigantism, after puberty acromegaly; deficiency gives dwarfism. Thyroid: goitre from iodine deficiency, cretinism in children, hyperthyroidism with weight loss and palpitations. Insulin deficiency causes diabetes mellitus with sugar in urine, thirst and frequent urination; ADH deficiency causes diabetes insipidus with large dilute urine; excess cortisol causes Cushing's syndrome.
Worked example
A woman loses weight despite eating, feels hot, has a tremor and a rapid pulse. A high metabolic rate with sympathetic overactivity points to excess thyroxine, not diabetes: diabetes gives thirst, weight loss and high glucose but not heat intolerance or tremor.
Marks-losing traps
Insulin is a protein, so it is injected and not swallowed; ADH and aldosterone both conserve water but come from different glands; the pituitary is itself controlled by the hypothalamus.