Acromegalia and insipid diabetes
This is a hypothalamus and pituitary gland question! So, first, lets talk about those two and then we’ll talk about the two diseases in question.
The hypothalamus sits in the diencephalon of the brain below the thalamus. It is linked to the pituitary gland via the pituitary stalk and controls various metabolic and hormonal aspects of the body. The pituitary gland as an anterior and posterior lobe (so called adenohypophysis and neurohypophysis). The anterior lobe is derived from embryonic tissue from the developing mouth (Rathke pouch) and consists of granular tissue, meanwhile the posterior lobe is an extension of the neural tissue of the hypothalamus.
So, lets now review the hormones that are released from the hypothalamus-pituitary axis:
- Posterior pituitary hormones
- ADH released from hypothalamus - pituitary stores ADH for release - targets kidneys, sweat glands, circulatory system - effects water balance
- Oxytocin released from pituitary - targets female reproductive system - triggers uterine contractions during childbirth
- Anterior pituitary hormones
- GnRH triggers - LH which targets reproductive system and stimulates production of sex hormones by gonads
- GnRH also triggers - FSH release which targets the reproductive system and stimulates production of sperm and eggs
- TRH triggers - TSH which targets thyroid gland, which stimulates the release of thyroid hormone and regulates the metabolism
- Dopamine (from the hypothalamus) mainly inhibits - prolactin release which targets mammary glands and promotes milk production
- Growth Hormone release hormone triggers - release of growth hormone which targets liver, bone and muscles, inducing targets to produce insulin like growth factor (IGF) which stimulates body growth and a higher metabolic rate
- Corticotropin release hormone triggers - adrenocorticotropic hormone (ACTH) which targets the adrenal glands, which induces targets to produce glucocorticoids, which regulate metabolism and the stress response.
Hyperpituitarism is commonly due to a pituitary adenoma. Classic symptoms depend on the specific cells involved in the adenoma, although an overlap is not uncommon:
- Cushing’s syndrome (hypercorticortisolsm) - due to increased ACTH
- Acromegaly (excessive growth hormone)
- Prolactinoma (excessive prolactin) can lead to irregular lactation and decreased sex drive - Prolactinomas are the most common type of pituitary adenoma
- Hyperthyroidism (increased TSH) leads to nervousness, tachycardia, weight loss, fatigue and muscle weakness