CAPs Week 25 LO 1

HPO axis

100

A rapid increase in which hormone causes ovulation?

LH

200

Lack of which hormones triggers endometrial shedding and menstrual bleeding normally?

Oestrogen and progesterone 

300

Which hormones control the luteal phase?

Drop in oestrogen and rapid increase in progesterone

HPT axis

100

What are the two forms of thyroid hormone?

Thyroxine (T4) and triiodothyronine (T3)

200

What is the only positive feedback mechanism in the hypothalamic-pituitary-thyroid axis?

Hypothalamic TRH stimulating release of TSH by the anterior pituitary gland 

300

When could TSH results be misleading in thyroid dysfunction?

Secondary hypothyroidism (pituitary gland does not increase TSH despite low T3/T4). 

Drugs affecting pituitary function can depress TSH independent of thyroid function. 

Hypothyroidism

100

What are the main presentations in AFAB of hypothyroidism?

Heavy menstrual bleeding with irregular cycles, weight gain (hyperprolactinaemia, lowered metabolism), fatigue, cold intolerance, hair loss

200

How does hypothyroidism lead to annovulation? 

Increased TRH increases prolactin which decreases GnRH. 

Decreased GnRH decreases LH and FSH

300

How do SHBG levels change in hypothyroidism and what effect does this have on menstrual bleeding? 

Decreased SHBG = increased free oestrogen = heavy bleeding

Hyperthyroidism

100

What are the main presentations in AFAB of hyperthyroidism? 

Infrequent or no periods, heat intolerance, weight loss, anxiety, infertility

200

In hyperthyroidism, why do patients experience weight loss as well as increased appetite?

Basal metabolic rate is increased so even though you eat more your metabolism is burning body fat and calories at a faster rate. 

300

Which autoimmune disease is the most common form of hyperthyroidism, and what are the effectors called?

Graves disease, thyroid stimulating immunoglobulins