Endocrine System: Pituitary Hormones, HPA Axis & Reproduction

What hormones are released by the anterior pituitary gland?

Prolactin, Gonadotropins (FSH and LH), Thyroid-stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), and Growth hormone.

What is the role of Adrenocorticotropic hormone (ACTH)?

ACTH acts on the adrenal cortex to regulate salt/carbohydrate metabolism and inflammatory reactions.

What does Luteinizing Hormone (LH) regulate?

LH acts on the gonads (ovaries and testes) to regulate reproduction.

What is the function of Follicle-stimulating hormone (FSH)?

FSH stimulates the growth of ovarian follicles and spermatogenesis in testes.

What hormone stimulates the thyroid gland?

Thyroid-stimulating hormone (TSH).

What are the hormones secreted by the posterior pituitary gland?

Oxytocin and Vasopressin (Antidiuretic Hormone / ADH).

Where are posterior pituitary hormones synthesized?

They are made by neuroendocrine cells in the hypothalamus.

What is the role of Oxytocin?

Oxytocin is involved in labor initiation, milk letdown reflex, orgasm, and maternal bonding.

What does Vasopressin (ADH) do?

It promotes water conservation and increases blood pressure.

What activates the HPA Axis?

The HPA Axis is activated by stress, pain, and negative emotions.

What is negative feedback in hormone regulation?

Negative feedback is when the final hormone produced feeds back to inhibit further hormone release from the hypothalamus and/or anterior pituitary.

What hormones are involved in the menstrual cycle?

FSH and LH from the anterior pituitary stimulate the ovaries.

During which phase of the menstrual cycle is fertility highest?

Fertility is highest during the periovulatory phase.

How do oral contraceptives block pregnancy?

They prevent ovulation by inhibiting the release of FSH and LH.

What are the three main types of hormones?

Peptide/Protein hormones, Amine hormones, and Steroid hormones.

What type of receptors do protein and peptide hormones use?

Metabotropic receptors on the cell membrane.

What type of receptors do steroid hormones use?

Intracellular receptors.

Why can't protein and peptide hormones use intracellular receptors?

They are not lipid-soluble and cannot diffuse through cell membranes.

What is the synthesis pathway for sex hormones starting from cholesterol?

Cholesterol -> Progesterone -> Testosterone -> Estradiol or Dihydrotestosterone (DHT).

What is the role of testosterone in hormone action?

Testosterone can exert effects at androgen receptors directly or at estradiol receptors after conversion.

What are the organizing effects of hormones?

Organizing effects are permanent changes in the body structure and function due to hormones.

What are the activating effects of hormones?

Activating effects are temporary changes in behavior or physiology due to hormones.

What is the role of the hypothalamus in hormone regulation?

The hypothalamus releases hormones that stimulate the anterior pituitary to release tropic hormones.

What triggers the milk letdown reflex?

Oxytocin release during breastfeeding.

What is the function of Prolactin?

Prolactin stimulates milk production in the mammary glands.

What are the peripheral actions of ACTH?

ACTH stimulates the adrenal cortex to produce cortisol and other hormones.

What hormones do the testes and ovaries release?

Testes release testosterone; ovaries release estradiol and progesterone.