Gonadotropins/Thyroid Set 12

What are the pituitary gonadotropins?

What are the pituitary gonadotropins?

LH = Luteinizing hormone

FSH = Follicle stimulating hormone

What does the Gonadotropin releasing hormone (GnRH), LH, and FSH regulate?

• Sexual differentiation

• Sex steroid production

• Fertility

How does LH and FSH affect women?

FSH promotes follicular development

LH promotes ovulation

How does LH and FSH affect men?

LH stimulates testosterone production from Leydig cells in the testes

FSH is required for spermatogenesis

What do estradiol, progesterone, and testosterone do?

Effects pituitary and hypothalamus

Negative feedback

Reduces LH and FSH release

What would cause a defect in reproductive function?

◦Primary failure of gonads

–serum gonadotropin concentrations will be high

◦Primary failure of hypothalamus or pituitary

–serum gonadotropin concentrations will be low

What does the thyroid stimulating hormone stimulate?

Production of T3 and T4

Which thyroid hormone is capable of exerting a biological affect?

Free hormone

The bound hormone is not able to enter the cell

T - uptake

The addition of labeled T3 or T4 to the serum

Saturates unbound TBG sites

Resin takes up excess T3 or T4

Low uptake

Increase unbound TBG

High uptake

Decrease unbound TBG

[total T4] * % Tuptake

FT4 Index

[total T3] * %Tuptake

FT3 Index

Resin takes up excess (unbound) T in an amount….

INVERSELY related to the amount of free binding sites

Which hormone is this?:

• Stimulated by TRH

• Inhibited by T4 and T3

TSH

Are more thyroid disorders primary or secondary?

Primary

Diagnosis?

TSH : Down

T4: Up

T-up: Up

FTI: Up

Primary hyperthyroid

Diagnosis?

TSH : Up

T4: Down

T-up: Down

FTI: Down

Primary Hypothyroid

Diagnosis?

TSH : Up

T4: Up

T-up: Up

FTI: Up

Secondary hyperthyroid

Diagnosis?

TSH : Down

T4: Down

T-up: Down

FTI: Down

Secondary hypothyroid

Diagnosis?

TSH : nl

T4: Up

T-up: Down

FTI: nl

Increased TBG

Diagnosis?

TSH : nl

T4: Down

T-up: Up

FTI: nl

Decreased TBG

What causes elevated TBG?

Pregnancy, birth control pills, other high estrogen states

What causes decreased TBG?

chronic liver disease, other low protein states

Best screening test for thyroid disorders?

TSH

Normal TSH levels

0.3 - 5.0

TSH > 5.0

FT4

TSH < 0.3

FT4*

*Consider FT3

Primary hypothyroidism

• Autoimmune with lymphocytic infiltration and destruction of the thyroid gland

• can be caused by thyroidectomy or post treatment for Grave’s disease with radioactive iodine

Hashimoto’s thyroiditis

Associated with circulating antibodies to thyroglobulin

Symptoms of Moderate Primary hypothyroidism

cold intolerance, weight gain, thinning of hair, voice changes, and other basic metabolic processes

Severe hypothyroidism

• may develop life threatening myxedema coma​

• replacement thyroid hormone is given very slowly to prevent metabolic collapse

Grave’s Hyperthyroidism

• less common

• Grave’s disease

• LATS, IgG immunoglobulin directed against TSH receptor, mediates thyroid stimulation of Grave’s disease

Signs and symptoms of Grave’s disease

hand tremors, heat intolerance, weight loss, increased appetite, warm moist skin, stare and lid lag

Treatment of Grave’s disease

Thyroid ablation by surgery or radioactive iodine, or chemical blockage of hormone production