The pituitary and hypopituitarism

Abstract

• The pituitary is formed of two anatomically and embryologically distinct lobes: ◦ anterior pituitary: which secretes growth hormone (GH), gonadotropins (luteinizing hormone (LH) and follicle-stimulating hormone (FSH)), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), and prolactin ◦ posterior pituitary: which secretes vasopressin and oxytocin. • Hypopituitarism is deficiency of one or more pituitary hormones. Some hormones, e.g. GH (LH/FSH), are more likely to present with isolated deficiencies, while others, e.g. TSH, ACTH, are more often found as part of multiple pituitary hormone deficiency (MPHD). • Deficiencies may be congenital (including genetic) or acquired; secondary to tumour, trauma, infiltration, infection, or irradiation. • GH deficiency: ◦ diagnosed using a combination of clinical, radiological, and biochemical assessment (including GH stimulation testing) ◦ treatment is with GH (including if necessary into adulthood). • LH/FSH deficiency: ◦ If acquired, often one of the first anterior pituitary hormones to be lost. ◦ Congenital forms: ■ present with cryptorchidism and/or micropenis in males ■ may occur in isolation, or in association with anosmia (Kallmann and CHARGE syndromes). ◦ Treatment: sex steroid therapy to induce secondary sexual characteristics, and recombinant FSH/LH to induce fertility potential. • ACTH deficiency: ◦ Unlike primary adrenal problems, hyperpigmentation does not occur. ◦ Although mineralocorticoid production is preserved, hyponatraemia may still occur. ◦ Treatment is with hydrocortisone. • TSH deficiency: ◦ TSH may be low, normal, or raised (but inappropriate for free thyroxine level). ◦ Treatment is with thyroxine. • Vasopressin deficiency: ◦ produces cranial diabetes insipidus ◦ treatment is with DDAVP (orally or nasally). • Prolactin and oxytocin deficiency rarely produce clinical problems.