Side by side
| Compared | Hypothalamus | Pituitary gland |
|---|---|---|
| Where it is | At the base of the brain, below the thalamus, forming the floor and lower walls of the third ventricle; part of the diencephalon. [1] | Below the hypothalamus at the base of the brain, attached to it by the pituitary stalk (infundibulum) and seated in the sella turcica, a saddle-shaped hollow of the sphenoid bone. In humans it is about the size of a chickpea and weighs on average 0.5 g. [2] |
| What it does | Links the nervous system to the endocrine system; it regulates body temperature, hunger, thirst, sleep cycles and the release of pituitary hormones. [1] | Releases hormones that regulate growth, blood pressure, metabolism, reproduction, water balance and the other endocrine glands such as the thyroid and adrenal glands. [2] |
| Connects with | Its neurons make oxytocin and vasopressin and send them along their axons, down the stalk, to the posterior pituitary; it sends releasing and inhibiting hormones to the anterior pituitary. [1][4] | Its anterior lobe is reached by the hypophyseal portal system, blood vessels carrying the hypothalamus’s hormones; its posterior lobe is made of nerve fibres from the hypothalamus. [5][2] |
| Size measured from the model | 18 mm front to back, 20 mm top to bottom, 17 mm side to side [3] | 10 mm front to back, 13 mm top to bottom, 12 mm side to side [3] |
Size is the box each part fits in on this one model (hypothalamus; pituitary gland), not its volume. Real brains vary.
How far apart are they?
Measured from the model [3], from the hypothalamus to the pituitary gland:
- Centre to centre: 14 mm in a straight line.
- The centre of the pituitary gland is 5 mm further forward, 13 mm lower and the same distance from the midline than the centre of the hypothalamus.
- Nearest points of the two shapes: under 1 mm apart.
A “centre” here is the average position of the points on the part’s 3D surface, so for a curved part such as a C shape it can sit outside the part itself. The nearest-points figure is measured between the corners of the simplified meshes, so a gap of 2 or 3 mm or less is within the model’s coarseness: read it as “touching or nearly so”.
How to tell them apart
- Brain tissue or gland: the hypothalamus is a region of the brain itself, while the pituitary’s front part (the anterior pituitary) is glandular tissue that develops from the roof of the mouth (Rathke’s pouch) and only its back part (the posterior pituitary) grows down from the brain. [2][6]
- The posterior pituitary makes no hormones of its own: it stores and releases the oxytocin and vasopressin made in the hypothalamus. [4]